A few weeks ago, my dog Lucy found a tube of printing ink and chewed it up. This resulted in some inky black paws! It was an oil-based ink, and soap and water wasn’t getting it out of her fur. So I mixed equal parts vegetable oil and soap in the palm of my hand and washed her feet with that. The ink came out!
Why does vegetable oil help remove ink?
To answer this question, we need to understand the wonderful concept of “hydrophobicity”. Hydrophobicity is a measure of how much a material “hates” water. Oil, grease, wax and oil-based ink are all hydrophobic. They do not mix with water at all. The opposite of hydrophobic is hydrophilic — meaning water loving — and that refers to any material that “loves” water — such as sugar, salt, alcohol, vinegar and antifreeze to name a few examples.
So what is the molecular basis for hydrophobicity? It all comes down to the quirky personality of water. You know the age old addage, “opposites attract”. Well, it is true on a molecular level, too! For example, sodium ion has a positive charge, and chloride ion has a negative charge — mix them together and you get salt. All of the substances I listed as hydrophilic (water loving) are either charged overall (such as the ions in salt) or have regions of charge (as in alcohol or antifreeze).
Hydrophobic substances do not have any charges. This means they are usually made of chemicals that have lots of carbon atoms but no oxygen atoms. You may have heard terms such as “unsaturated fats” or “saturated fats” — these words describe the arrangement of the strings of carbon atoms that are in fat.
What makes water quirky is that even though it has no charge, it loves other charged molecules. This is because water can quickly convert from H2O (with no charge) to just HO (with a negative charge) or to H3O (with a positive charge). In addition, although H2O is not charged, it is a little bit “polar” — this means that on one side it has a slight positive charge and on the other it has a slight negative charge. The flexible distribution of charges in water means that it can surround other charged molecules with ease (which is what happens when something hydrophilic dissolves in water).
What happens if you take a long molecule and put a charge at one end, but make the rest of it hydrophobic? You’ve created soap! The soap molecule can wrap up an oily molecule. When it does that, the charged part of the soap is the only thing left on the outside — so now water can surround it and make it dissolve.
When Lucy’s paw was covered in black ink, there was too much oily ink for the soap to penetrate. Plus, ink is a very thick sludgy mixture of oils. Vegetable oil, on the other hand is runnier and can be cleaned with soap more easily. By mixing vegetable oil in, the ink molecules mixed with the oil (because they are both hydrophobic) and loosened it away from Lucy’s fur. Then the soap and water was able to lift them both away.
Try mixing vegetable oil with dish soap next time you have grease or pine sap stuck in your hair or on your hands.
Category: Uncategorized
Categories
A/D conversion
I’ve gotten the A/D converter on the Microchip PIC P12F675 to work. The pulse width modulation technique is allowing me to simulate different intensities of light. What you do is send extremely fast pulses of light on and off. Your eye “averages” these out to appear as a middle intensity brightness.
Here is a movie:
Here is the source code:
1 ;Software License Agreement 2 ; 3 ;The software supplied herewith by Microchip Technology 4 ;Incorporated (the "Company") is intended and supplied to you, the 5 ;Company~Rs customer, for use solely and exclusively on Microchip 6 ;products. The software is owned by the Company and/or its supplier, 7 ;and is protected under applicable copyright laws. All rights are 8 ;reserved. Any use in violation of the foregoing restrictions may 9 ;subject the user to criminal sanctions under applicable laws, as 10 ;well as to civil liability for the breach of the terms and 11 ;conditions of this license. 12 ; 13 ;THIS SOFTWARE IS PROVIDED IN AN "AS IS" CONDITION. NO WARRANTIES, 14 ;WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, BUT NOT LIMITED 15 ;TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 16 ;PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. THE COMPANY SHALL NOT, 17 ;IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL OR 18 ;CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER. 19 ;**************************************************************************** 20 ;Filename: atod.asm 21 ;Author: Ruan Lourens 22 ;Date: 1.03.03 23 ;Version: 1.0 (A/D Version) 24 ;Description: This is an ASSEMBLY written program designed to show the user 25 ; a timer driven analog-to-digital conversion.It is based on the 26 ; interrupt driven conversionLED State Machine used in 27 ; tutorial #3. 28 ;**************************************************************************** 29 ;Revision History 30 ;**************************************************************************** 31 32 33 list p=12F675 ; list directive to define processor 34 #include <p12f675.inc> ; processor specific variable definitions 35 ;#include "atod.h" 36 errorlevel -302 ; suppress message 302 from list file 37 38 __CONFIG _CP_OFF & _CPD_OFF & _BODEN_OFF & _MCLRE_OFF & _WDT_OFF & _PWRTE_ON & _INTRC_OSC_NOCLKOUT 39 40 ; '__CONFIG' directive is used to embed configuration word within .asm file. 41 ; The lables following the directive are located in the respective .inc file. 42 ; See data sheet for additional information on configuration word settings. 43 44 ;**************************************************************************** 45 ;Defines 46 ;**************************************************************************** 47 #define BANK1 bsf STATUS,RP0 ; Bank1 48 #define BANK0 bcf STATUS,RP0 ; Bank0 49 #define LED1TRIS b'11001111' 50 #define LED2TRIS b'11001111' 51 #define LED3TRIS b'11101011' 52 #define LED4TRIS b'11101011' 53 #define LED5TRIS b'11011011' 54 #define LED6TRIS b'11011011' 55 #define LED7TRIS b'11111001' 56 #define LED8TRIS b'11111001' 57 #define LED1ON b'00010000' 58 #define LED2ON b'00100000' 59 #define LED3ON b'00010000' 60 #define LED4ON b'00000100' 61 #define LED5ON b'00100000' 62 #define LED6ON b'00000100' 63 #define LED7ON b'00000100' 64 #define LED8ON b'00000010' 65 #define NUMBEROFBITS .8 66 #define ANSelect b'00010001' ;Used to configure AD 67 #define ADControl b'00000001' ;Used to configure AD 68 69 LEDREGISTER EQU 0x31 70 71 mcount EQU 22h 72 ncount EQU 23h 73 new_tris EQU 24h 74 new_gpio EQU 25h 75 brightness_num EQU 26h 76 brightness_den EQU 27h 77 brightness_dat EQU 28h 78 IS_ON_BIT EQU 0 79 brightness_count EQU 29h 80 temp EQU 30h 81 ALL_OFF_TRIS EQU b'11111111' 82 83 ;**************************************************************************** 84 ;General Purpose Registers (GPR's) 85 ;**************************************************************************** 86 ; UDATA_SHR 87 WTEMP res 1 ; register used in Interrupt Routine 88 STATUSTEMP res 1 ; register used in Interrupt Routine 89 PCLATHTEMP res 1 ; register used in Interrupt Routine 90 FSRTEMP res 1 ; register used in Interrupt Routine 91 FLAGS res 1 ; register used to set flags 92 93 ;**************************************************************************** 94 ;Reset Vector 95 ;**************************************************************************** 96 ORG 0x000 ; processor reset vector 97 nop ; Inserted For ICD2 Use 98 goto Init ; go to beginning of program 99 100 ;**************************************************************************** 101 ;Interrupt Vector - Interrupts only active during animation sequence 102 ; - Interrupt Sources: 1. TIMER0 Overflow 103 ; 104 ;FLAGS register - bit0: 1 = A/D will be serviced, 0 = Display will be serviced 105 ; 106 ;**************************************************************************** 107 ORG 0x004 ; interrupt vector location 108 Isr 109 movwf WTEMP ;Save off current W register contents 110 movf STATUS,w 111 clrf STATUS ;Force to page0 112 movwf STATUSTEMP 113 ;movf PCLATH,w 114 ;movwf PCLATHTEMP ;Save PCLATH 115 ;movf FSR,w 116 ;movwf FSRTEMP ;Save FSR 117 118 119 ;**************************************************************************** 120 ;Interrupt Source Checks 121 ;**************************************************************************** 122 Timer0InterruptCheck 123 BANK1 ; BANK1 124 movf INTCON,w 125 andlw 0x20 126 btfsc STATUS,Z ;Is T0IE Set? 127 goto Next1 ;No 128 movf INTCON,w ;Yes 129 andlw 0x04 130 btfss STATUS,Z ;Is TOIF Set? 131 goto Timer0Interrupt ;Yes 132 133 Next1 134 GPIFInterruptCheck 135 movf INTCON,w 136 andlw 0x08 137 btfsc STATUS,Z ;Is GPIE Set? 138 goto Next2 ;No 139 movf INTCON,w ;Yes 140 andlw 0x01 141 btfss STATUS,Z ;Is GPIF Set? 142 goto GPIFInterrupt ;Yes 143 144 Next2 145 GP2_INT_ExternalInterruptCheck 146 movf INTCON,w 147 andlw 0x10 148 btfsc STATUS,Z ;Is INTE Set? 149 goto Next3 ;No 150 movf INTCON,w ;Yes 151 andlw 0x02 152 btfss STATUS,Z ;Is INTF Set? 153 goto GP2_INTExternalInterrupt;Yes 154 155 Next3 156 PeripheralInterruptCheck 157 movf INTCON,w 158 andlw 0x40 159 btfsc STATUS,Z ;Is PEIE Set? 160 goto EndIsr ;No 161 162 Next4 163 EEIFInterruptCheck 164 movf PIE1,w 165 andlw 0x80 166 btfsc STATUS,Z ;Is EEIE Set? 167 goto Next5 ;No 168 BANK0 ;Yes 169 movf PIR1,w 170 BANK1 171 andlw 0x80 172 btfss STATUS,Z ;Is EEIF Set? 173 goto EEPROMInterrupt;Yes 174 175 Next5 176 ADIFInterruptCheck 177 movf PIE1,w 178 andlw 0x40 179 btfsc STATUS,Z ;Is ADIE Set? 180 goto Next6 ;No 181 BANK0 182 movf PIR1,w 183 BANK1 184 andlw 0x40 185 btfss STATUS,Z ;Is ADIF Set? 186 goto A_DConverterInterrupt;Yes 187 188 Next6 189 CMIFInterruptCheck 190 movf PIE1,w 191 andlw 0x08 192 btfsc STATUS,Z ;Is CMIE Set? 193 goto Next7 ;No 194 BANK0 ;Yes 195 movf PIR1,w 196 BANK1 197 andlw 0x08 198 btfss STATUS,Z ;Is CMIF Set? 199 goto ComparatorInterrupt;Yes 200 201 Next7 202 TMR1IFInterruptCheck 203 movf PIE1,w 204 andlw 0x01 205 btfsc STATUS,Z ;Is TMR1IE Set? 206 goto EndIsr ;No 207 BANK0 ;Yes 208 movf PIR1,w 209 BANK1 210 andlw 0x01 211 btfss STATUS,Z ;Is TMR1IF Set? 212 goto Timer1Interrupt ;Yes 213 goto EndIsr ;No 214 215 Timer0Interrupt ;Interrupt every 1024 uS 216 BANK0 ;BANK0 217 btfsc FLAGS,0 ;Check if A/D functions will be serviced or the display routine 218 call AD_Functions ;Yes, service A/D 219 BANK0 ;BANK0 220 btfss FLAGS,0 ;Check if Display functions will be serviced 221 call Display ;Yes, goto Display 222 BANK0 ;BANK0 223 movlw b'00000001' 224 xorwf FLAGS,F ;Toggle FLAGS,1 225 BANK1 ;BANK1 226 bcf INTCON,T0IF ;Clear TMR0 Interrupt Flag 227 goto EndIsr 228 229 Display 230 decfsz brightness_count,f 231 goto activate_leds 232 goto toggle_on_off 233 toggle_on_off: 234 movlw b'11111111' 235 xorwf brightness_dat,f 236 btfsc brightness_dat,IS_ON_BIT 237 goto store_off_time 238 goto store_on_time 239 store_on_time: 240 movfw brightness_num 241 movwf brightness_count 242 goto activate_leds 243 store_off_time: 244 movfw brightness_den 245 movwf brightness_count 246 activate_leds: 247 btfsc brightness_dat,IS_ON_BIT 248 goto show_black 249 goto show_lights 250 show_black: 251 movlw b'11111111' 252 bsf STATUS,RP0 ;Bank 1 253 movwf TRISIO ;and set GP<5:4,1:0> 254 bcf STATUS,RP0 ;Bank 0 255 movlw b'00000000' 256 movwf GPIO 257 goto end_of_intr 258 show_lights: 259 movfw new_tris; 260 bsf STATUS,RP0 ;Bank 1 261 ;movlw b'11001111' 262 movwf TRISIO ;and set GP<5:4,1:0> 263 bcf STATUS,RP0 ;Bank 0 264 movfw new_gpio 265 ;movlw b'00010000' 266 movwf GPIO 267 end_of_intr: 268 return 269 270 271 272 273 GPIFInterrupt 274 goto EndIsr 275 276 GP2_INTExternalInterrupt 277 goto EndIsr 278 279 EEPROMInterrupt 280 goto EndIsr 281 282 A_DConverterInterrupt 283 goto EndIsr 284 285 ComparatorInterrupt 286 goto EndIsr 287 288 Timer1Interrupt 289 290 EndIsr 291 clrf STATUS ;Select Bank0 292 ;movf FSRTEMP,w 293 ;movwf FSR ;Restore FSR 294 ;movf PCLATHTEMP,w 295 ;movwf PCLATH ;Restore PCLATH 296 movf STATUSTEMP,w 297 movwf STATUS ;Restore STATUS 298 swapf WTEMP,f 299 swapf WTEMP,w ;Restore W without corrupting STATUS bits 300 retfie ;Return from interrupt 301 302 303 ;**************************************************************************** 304 ;AD_Functions 305 ;**************************************************************************** 306 AD_Functions 307 BANK0 ;BANK0 308 movf ADRESH,W ;Move the most significant byte of A/D Result to W 309 movwf LEDREGISTER ;The A/D result is moved to LEDREGISTER and will be displayed 310 bsf ADCON0,GO ;Start A/D 311 return 312 313 ;**************************************************************************** 314 ;Initialization 315 ;**************************************************************************** 316 Init 317 ;call 0x3FF ; retrieve factory calibration value 318 ; comment instruction if using simulator, ICD2, or ICE2000 319 BANK1 320 movwf OSCCAL ; update register with factory cal value 321 ;call InitLED ;Initialize LED Routine Variables 322 movlw b'00000001' 323 movwf TRISIO ;Tri-State All Inputs 324 BANK0 ;BANK 0 325 clrf GPIO ;Clear Port 326 movlw b'00100000' 327 movwf GPIO 328 329 BANK1 ;BANK 1 330 clrf VRCON ;Vref Off 331 BANK0 ;BANK 0 332 clrf TMR0 333 movlw 0x07 334 movwf CMCON ;Comparator Off 335 336 BANK1 ;BANK 1 337 movlw b'10000001' 338 movwf OPTION_REG ;TIMER0 Prescaler = 4 and pull-ups disabled 339 bsf INTCON,T0IE ;Interrupt on TIMER0 Overflow Enabled 340 bcf INTCON,T0IF ;Clear TIMER0 Overflow Interrupt Flag 341 bsf INTCON,GIE ;Turn on Global Interrupts 342 movlw ANSelect 343 movwf ANSEL ;Configure AN0 & prescale to A/D 344 345 BANK0 ;BANK 0 346 movlw ADControl 347 movwf ADCON0 ;Select AN0, Left justified & enables A/D 348 NOP 349 NOP 350 NOP 351 NOP ; Give 4 uS delay before starting A/D 352 bsf ADCON0,GO ; Start A/D 353 354 ;**************************************************************************** 355 ;MAIN - Main Routine 356 ;**************************************************************************** 357 Main 358 movlw 0x02 359 movwf brightness_num 360 movlw 0x1F 361 movwf brightness_den 362 movlw 0xFF 363 movwf brightness_count 364 go 365 ; D0 366 movlw b'11001111' 367 movwf new_tris 368 movlw b'00010000' 369 movwf new_gpio 370 call delay 371 ; D0 372 movlw b'11001111' 373 movwf new_tris ;and set GP<5:4,1:0> 374 movlw b'00100000' 375 movwf new_gpio 376 call delay 377 ; D0 378 movlw b'11101011' 379 movwf new_tris ;and set GP<5:4,1:0> 380 movlw b'00010000' 381 movwf new_gpio 382 call delay 383 ; D0 384 movlw b'11101011' 385 movwf new_tris ;and set GP<5:4,1:0> 386 movlw b'00000100' 387 movwf new_gpio 388 call delay 389 ; D7 390 movlw b'11111001' 391 movwf new_tris ;and set GP<5:4,1:0> 392 movlw b'00000010' 393 movwf new_gpio 394 call delay 395 ; D6 396 movlw b'11111001' 397 movwf new_tris ;and set GP<5:4,1:0> 398 movlw b'00000100' 399 movwf new_gpio 400 call delay 401 ; D5 402 movlw b'11011011' 403 movwf new_tris ;and set GP<5:4,1:0> 404 movlw b'00000100' 405 movwf new_gpio 406 call delay 407 ; D0 408 movlw b'11011011' 409 movwf new_tris ;and set GP<5:4,1:0> 410 movlw b'00100000' 411 movwf new_gpio 412 call delay 413 goto go 414 415 416 ;delay loop 417 delay movlw 0x01 418 movwf temp 419 movwf brightness_num 420 loadm2 movlw 0x2f 421 movwf mcount 422 loadn2 movfw LEDREGISTER 423 addlw 1 424 movwf ncount 425 repeat2 426 decfsz ncount,f 427 goto repeat2 428 decfsz mcount,f 429 goto loadn2 430 incf brightness_num,f 431 movlw 0x13 432 movwf brightness_den 433 movfw brightness_num 434 subwf brightness_den,f 435 incf brightness_den,f 436 movlw 0x13 437 xorwf brightness_num,w 438 movwf temp 439 incf temp,f 440 decfsz temp,f 441 goto loadm2 442 goto delay2 443 delay2 movlw 0x13 444 movwf brightness_num 445 loadm movlw 0x2f 446 movwf mcount 447 movlw 0x13 448 movwf brightness_den 449 movfw brightness_num,f 450 subwf brightness_den,f 451 incf brightness_den,f 452 loadn movfw LEDREGISTER 453 addlw 1 454 movwf ncount 455 repeat 456 decfsz ncount,f 457 goto repeat 458 decfsz mcount,f 459 goto loadn 460 decfsz brightness_num,f 461 goto loadm 462 return 463 464 465 ; initialize eeprom locations 466 467 ORG 0x2100 468 DE 0x00, 0x01, 0x02, 0x03 469 470 471 END ; directive 'end of program' 472
I have to share my solution for this problem I was having. My PIC controller programmer only works on Windows (for the time being) because of various technical difficulties (I’ll spare you the details). I only have a Mac at home.
So I plugged the pic controller programmer into my Windows machine at work and turned on Remote Desktop. With Remote Dekstop, I can control my Windows machine from home.
Then I pointed the iSight camera attached to my work Mac at the programmer.
Finally, if I remote desktop into both machines at work, I can dial myself up on iChatAV and get a view of the programmer (and the important 10 LEDs). I can also run the programmer software on the Windows machine to upload new software into the PIC.
W00T!
Categories
Chlorophyll Fluorescence
In a discussion today I was reminded of one of my favorite experiments from college plant physiology class. We were discussing the light harvesting apparatus (LHA) of a plant cell. The molecular organization of this system relies on the primary light collecting molecule chlorophyll. Chlorophyll acts to trap light radiation and convert that into what is called an “excited electron”. This is sort of like electricity. A field of chlorophyll molecules are attached to the chloroplast internal membrane. They pass the excited electrons around until the reach some molecular machines that use that electron to create sugar. The process of making sugar is amazingly complicated, involving a proton gradient, electron carrying molecule (NADPH) and the biological “currency” of the cell, ATP. I’ll spare you the details (for now, moo hoo hah aha ahhaa!).
Anyhow, the interesting thing about chlorophyll in this case is that when it is not attached to the rest of the LHA, the excited electron doesn’t have anywhere to go. So eventually in that case, the electron will become unexcited and in so doing emit some light. However, since there is energy loss in this system, the emitted light is of a lower energy — so it is redder than the light it absorbed.
Plants look green because of the light absorbing characteristics of chlorophyll. Chlorophyll absorbs red and blue light. The water in the plant leaf is shiny and reflects the rest of the light — green.
Okay, with that background info we can go back to the interesting experiment. You can try this at home, but be very careful because acetone is flamable, and blenders can create sparks. Be sure to have fire extinguisher at the ready and also take note that I take no responsibility for death, blindness or dismemberment that results. On the other hand, I was able to do this experiment successfully with a four year old sister and my mother-in-law.
Take some spinach — or any green leafy plant, grass clippings work too. Put it in the blender with some acetone (nail polish remover works). Blend for a little while until it makes a rich green juice. Now strain out the plant matter and reserve the precious green liquid. If you look through the liquid at a bright light source, you will see the light that is not absorbed by the chlorophyll — green is not absorbed so the liquid looks green.
Now for the really cool part. Look at the liquid when it is lit by a strong light from the side. Sunlight works the best, but light from an overhead projector is okay, too. The chlorophyll absorbs the light and then emits light back out. But it emits a different color! The solution will be a deep ruby red. It is really wild to watch the color change depending on your point of view.
Categories
Das Blinken Lights
Well, I’ve given up (for the time being) on how to use my Macintosh to program the PIC controller. I took my lunch hour today at work to program my PIC p12F675 on the PICKit 1 Flash Starter Kit to blink its lights in a circular fashion. Since there is a lack of good info about this on the web, per my new initiative to inform the world (lol) I’m going to say exactly how I did it.
First, I installed the gnu pic utilities — of which I’m using gpasm to “assemble” my code into pic bytecode. (See below for the code.)
Next I compiled the code like this:
gpasm –dos -pp12F675 –hex-format inhx32 gp2.asm
It is necessary to add the –dos option since the upload program I use is a Windows program. Oh and by the way everything so far is Mac friendly. Now copy the resulting .hex file onto your windows box and upload it using the PICkit(tm) 1 FLASH Starter Kit application. I think I used the “Baseline Flash” instead of the “Classic” version. Control – I Imports, and Control – W writes.
Be sure you have the right kind of PIC — for my program I used a p12f675.
Voila!
Double click to replay if there is no controller.
Can’t see the video above? Click
here to download our video file, then launch it from your desktop.
Still can’t
see the video? Install Apple’s free QuickTime player.
Here is the code, for those at home who wish to duplicate my experiment.
1 ; This file is a basic code template for assembly code generation * 2 ; on the PICmicro PIC12F675. This file contains the basic code * 3 ; building blocks to build upon. * 4 ; * 5 ; If interrupts are not used all code presented between the ORG * 6 ; 0x004 directive and the label main can be removed. In addition * 7 ; the variable assignments for 'w_temp' and 'status_temp' can * 8 ; be removed. If the internal RC oscillator is not implemented * 9 ; then the first four instructions following the label 'main' can * 10 ; be removed. * 11 ; * 12 ; Refer to the MPASM User's Guide for additional information on * 13 ; features of the assembler (Document DS33014). * 14 ; * 15 ; Refer to the respective PICmicro data sheet for additional * 16 ; information on the instruction set. * 17 ; * 18 ;********************************************************************** 19 ; * 20 ; Filename: xxx.asm * 21 ; Date: * 22 ; File Version: * 23 ; * 24 ; Author: * 25 ; Company: * 26 ; * 27 ; * 28 ;********************************************************************** 29 ; * 30 ; Files required: * 31 ; * 32 ; * 33 ; * 34 ;********************************************************************** 35 ; * 36 ; Notes: * 37 ; * 38 ; * 39 ; * 40 ; * 41 ;********************************************************************** 42 43 list p=12f675 ; list directive to define processor 44 #include <p12f675.inc> ; processor specific variable definitions 45 46 errorlevel -302 ; suppress message 302 from list file 47 48 __CONFIG _CP_OFF & _CPD_OFF & _BODEN_OFF & _MCLRE_OFF & _WDT_OFF & _PWRTE_ON & _INTRC_OSC_NOCLKOUT 49 50 ; '__CONFIG' directive is used to embed configuration word within .asm file. 51 ; The lables following the directive are located in the respective .inc file. 52 ; See data sheet for additional information on configuration word settings. 53 54 55 56 57 ;***** VARIABLE DEFINITIONS 58 w_temp EQU 0x20 ; variable used for context saving 59 status_temp EQU 0x21 ; variable used for context saving 60 mcount EQU 22h 61 ncount EQU 23h 62 new_tris EQU 24h 63 new_gpio EQU 25h 64 65 66 67 68 69 70 ;********************************************************************** 71 ORG 0x000 ; processor reset vector 72 goto main ; go to beginning of program 73 74 75 ; (no interrupt) ORG 0x004 ; interrupt vector location 76 ; (no interrupt) movwf w_temp ; save off current W register contents 77 ; (no interrupt) movf STATUS,w ; move status register into W register 78 ; (no interrupt) movwf status_temp ; save off contents of STATUS register 79 ; (no interrupt) 80 ; (no interrupt) 81 ; (no interrupt); isr code can go here or be located as a call subroutine elsewhere 82 ; (no interrupt) 83 ; (no interrupt) 84 ; (no interrupt) movf status_temp,w ; retrieve copy of STATUS register 85 ; (no interrupt) movwf STATUS ; restore pre-isr STATUS register contents 86 ; (no interrupt) swapf w_temp,f 87 ; (no interrupt) swapf w_temp,w ; restore pre-isr W register contents 88 ; (no interrupt) retfie ; return from interrupt 89 90 91 ; these first 4 instructions are not required if the internal oscillator is not used 92 main 93 call 0x3FF ; retrieve factory calibration value 94 bsf STATUS,RP0 ; set file register bank to 1 95 movwf OSCCAL ; update register with factory cal value 96 bcf STATUS,RP0 ; set file register bank to 0 97 98 99 ; remaining code goes here 100 101 bcf STATUS,RP0 ;Bank 0 102 clrf GPIO ;Init GPIO 103 movlw 07h ;Set GP<2:0> to 104 movwf CMCON ;digital IO 105 bsf STATUS,RP0 ;Bank 1 106 clrf ANSEL ;Digital I/O 107 movlw 08h ;Set GP<3:2> as inputs 108 movwf TRISIO ;and set GP<5:4,1:0> 109 ;as outputs 110 bcf STATUS,RP0 ;Bank 0 111 112 go 113 ; D0 114 bsf STATUS,RP0 ;Bank 1 115 movlw b'11001111' 116 movwf TRISIO ;and set GP<5:4,1:0> 117 bcf STATUS,RP0 ;Bank 0 118 movlw b'00010000' 119 movwf GPIO 120 call delay 121 ; D0 122 bsf STATUS,RP0 ;Bank 1 123 movlw b'11001111' 124 movwf TRISIO ;and set GP<5:4,1:0> 125 bcf STATUS,RP0 ;Bank 0 126 movlw b'00100000' 127 movwf GPIO 128 call delay 129 ; D0 130 bsf STATUS,RP0 ;Bank 1 131 movlw b'11101011' 132 movwf TRISIO ;and set GP<5:4,1:0> 133 bcf STATUS,RP0 ;Bank 0 134 movlw b'00010000' 135 movwf GPIO 136 call delay 137 ; D0 138 bsf STATUS,RP0 ;Bank 1 139 movlw b'11101011' 140 movwf TRISIO ;and set GP<5:4,1:0> 141 bcf STATUS,RP0 ;Bank 0 142 movlw b'00000100' 143 movwf GPIO 144 call delay 145 ; D7 146 bsf STATUS,RP0 ;Bank 1 147 movlw b'11111001' 148 movwf TRISIO ;and set GP<5:4,1:0> 149 bcf STATUS,RP0 ;Bank 0 150 movlw b'00000010' 151 movwf GPIO 152 call delay 153 ; D6 154 bsf STATUS,RP0 ;Bank 1 155 movlw b'11111001' 156 movwf TRISIO ;and set GP<5:4,1:0> 157 bcf STATUS,RP0 ;Bank 0 158 movlw b'00000100' 159 movwf GPIO 160 call delay 161 ; D5 162 bsf STATUS,RP0 ;Bank 1 163 movlw b'11011011' 164 movwf TRISIO ;and set GP<5:4,1:0> 165 bcf STATUS,RP0 ;Bank 0 166 movlw b'00000100' 167 movwf GPIO 168 call delay 169 ; D0 170 bsf STATUS,RP0 ;Bank 1 171 movlw b'11011011' 172 movwf TRISIO ;and set GP<5:4,1:0> 173 bcf STATUS,RP0 ;Bank 0 174 movlw b'00100000' 175 movwf GPIO 176 call delay 177 goto go 178 179 180 ;delay loop 181 delay movlw 0x4f 182 movwf mcount 183 loadn movlw 0xff 184 movwf ncount 185 repeat decfsz ncount,f 186 goto repeat 187 decfsz mcount,f 188 goto loadn 189 return 190 191 ; initialize eeprom locations 192 193 ORG 0x2100 194 DE 0x00, 0x01, 0x02, 0x03 195 196 197 END ; directive 'end of program' 198 199
Oh, were you wondering how I got the nice formatting for the code? I used VIM like this
:runtime! syntax/2html.vim. Do :help 2html in VIM for more info.
Categories
PIC microcontroller
I’ve discovered an entirely new realm of geekiness in PIC microcontrollers. These inexpensive ( ~$2.00 ) computers can be programmed to control lights, motors or whatever and can also be controlled through switches or knobs. My mind is exploding with possibilities with what you can make with these. For example, the good old simon says toy, where lights flash in a random sequence which you have to remember, and then you press buttons in the same sequence back. Or a christmas decoration which twinkles. Or lights that zip in a pattern on a billboard sign. Or a robot that drives itself around towards a light source.
Help! I need some ideas of what my first project should be.
I’ve also noticed, as my friend Stacie the librarian preaches, that the internet is indeed a lousy place to find information. Thus as a public service to the world at large, I would like to publicly answer a question that took me about a half hour to figure out. With hope, Google will index this question and answer the future generations of geeks will be spared the pain.
Question: Where do you get GCC 3.1 for Mac OS X (Darwin) version 10.3 or higher?
Answer: It is in a package called gcc3.1.pkg on the XCode 1.5 disk image. You can download XCode from Apple if you set up a free Developer Connection user account.
Well, next I’m trying to use Fink to install libusb so I can build usb_pickit and hopefully get it to work with the PICKit 1 Onboard firmware version is 2.0.2. Apparently the Mac OS tools for the PICKit stopped working when Microchip updated the firmware — doh!
Categories
Fiesta!
Becka got me into this week’s drawing. This week the word was Fiesta and this is what I drew:
(click for full size)
Categories
Give me a caption
I drew this picture a few days ago. Can you think of a caption for the picture?
Categories
Pitch Black Mountain Dew
If you haven’t read the first entry in about pitch black mountain dew’s blue foam…
Well, after much eager anticipation, my analysis about why the bubbles on the weird pitch black mountain dew turn blue is complete. At the end of my previous post, I had a couple of ideas for some experiments to help clarify this issue. I’ve now finished my experiments and am happy to report that I think the mystery is solved!
I was able to collect a sample of the blue foam. This was difficult at first, because it doesn’t turn blue until it’s almost entirely gone. However, I discovered that if I shook the bottle up with the cap closed, and then carefully released some air, the soda would foam up inside the bottle. After a few moments, the foam in the bottle turned blue. Then I released some more air by opening the lid a small amount and collected some of the foam that ran out.
I blotted nine drops of the liquid from the blue foam and nine drops of regular soda onto a paper towel and let it dry for several days. Then I scanned the towel into Photoshop and drew rectangles around each drop and looked at the red and blue values for each
The picture doesn’t really do it justice, the difference is far more startling that that looks. But who am I to trust the human eye to discern differences? This table presents the raw data for the red and blue channels’ average pixel value as well as the ratio of the two, the averages of those six data sets and the p value from the Student’s T Test on the ratios.
| regular red | regular blue | foam red | foam blue | regular ratio | foam ratio | |
| 247 | 213 | 232 | 219 | 1.15962441 | 1.05936073 | |
| 248 | 209 | 229 | 224 | 1.18660287 | 1.02232143 | |
| 246 | 218 | 231 | 219 | 1.12844037 | 1.05479452 | |
| 240 | 210 | 229 | 222 | 1.14285714 | 1.03153153 | |
| 248 | 220 | 227 | 220 | 1.12727273 | 1.03181818 | |
| 241 | 209 | 228 | 221 | 1.15311005 | 1.03167421 | |
| 247 | 217 | 225 | 228 | 1.13824885 | 0.98684211 | |
| 240 | 220 | 232 | 221 | 1.09090909 | 1.04977376 | |
| 242 | 221 | 225 | 222 | 1.09502262 | 1.01351351 | |
| average | 244.333333 | 215.222222 | 228.666667 | 221.7777778 | 1.13578757 | 1.03129222 |
| std. Dev | 3.5 | 4.99444135 | 2.6925824 | 2.818589088 | 0.03022589 | 0.02251282 |
| p | 3.6661E-05 |
The T Test comes to the same conclusion as my eye — the colors are different!
The results of a second experiment were negative. When I mixed dish detergent with the soda and whipped it up using my nifty milk frother, the resulting foam bubbles did not turn blue. This suggests that my hypothesis advanced in the first posting about blue dye having the ability to diffuse into bubbles is not correct.
So what does this mean? The conclusion I have come to has to do with a technique known as column chromatography. Column chromatography passes a mixture through a tube that is packed with a material that has an affinity for some of the molecules in the mixture. This will slow the molecules down a little, so as water is washed through the tube the molecules come out the other end at different times. Typically a person will collect a few drops of water into a series of tubes (these are called “fractions”). Then you test each fraction to see what is in it. Using a variety of different columns you can actually purify things pretty well.
Anyhow, I had noticed that the foam only turns blue after the bubbles on top had been bursting for a while. This causes those bubbles near the top to turn back into liquid and flow through the foam underneath. The foam bubbles underneath act like a column, to which the blue dye apparently has a higher affinity than the red dye.
Sorry, I can’t write now – West Wing is starting!
Categories
The Pinhole Camera
You may know that I work for a software company that is highly respected for its digital imaging products. As a result, I’ve been trying to learn more about photography. For example,
Near Snail Lake, MN
As it turns out, there is a lot of science in photography. It is much more than I can discuss in a single entry — there is the chemistry of film, optics, exposure, not to mention the artistic concepts such as composition, mood, etc… Besides, I’m not much of an expert yet so I’m not really qualified to discuss most of that (yet!).
So let’s start out by considering the worlds simplest camera, the Pinhole camera. Once we understand that camera and its limitations, we can move on to understand why people use other kinds of cameras most of the time.
A pinhole camera is quite simple. It consists of a box with a large piece of photographic paper mounted at one end, and a very tiny hole that can be covered up at the other end.
A Pinhole Camera
We all know that light moves in a straight line. By using a tiny pinhole, each point on the film only sees a tiny piece of the outside world. I’ve drawn to small grey lines showing how the light from the tree passes through the pinhole to a corresponding point on the film. One incidental result of this is that the image is upside down on the film.
If you make the box longer, the image will get bigger. If you don’t believe me, draw a new pinhole to the right, and trace from the back of the box to see how much of the tree you’ll see on the film. You should see less of the tree — so the image is “zoomed in”. This is one fundamental concept of photography : The longer your focal length, the more zoomed in you are. In fact, when photographers talk about lenses, the talk about the focal length. For a standard camera, a typical lens might have a focal length of 30mm. My friend Jessie’s favorite lens is a 50mm, which is a little bit more zoomed in. A “fish eye” lens might be 15mm. A telephoto lens is in the range of 75 to 300 (or more) mm. 300mm is about a foot, which starts to be a pretty awkward length of lens hang off the front of your camera.
This raises an interesting side question : Why do you need zoom, can’t you just move closer to the subject? For some things that is true, a similar effect can be achieved by moving the camera closer to the subject. But in some cases, the use of zoom provides an important tool in how an image is composed. Consider a scene with a tree and the moon on the corner of the block. You are the photographer, and you stand in the intersection using different focal lengths on your pinhole camera. For this example, I’ll assume that you adjust the position of the camera so that the tree is the same size in each picture.
The same moon and tree picture taken with a very short focal length, medium focal length and long focal length
What you notice is a striking difference in composition. With the very short focal length (e.g. “zoomed all the way out” according to our “focal length / zoom” rule) distant objects (such as the moon) appear very far away. Also, things at the perifery of your vision are more prominent in the picture, such as the street extending away to your right and left. With a very long focal length (e.g. “zoomed all the way in”), distant objects appear larger relative to close objects. Also, objects in the perfery are absent as being “zoomed in” restricts your field of view.
There is a corollary to the “focal length / zoom” rule. As the focal length gets longer, less light makes it to the film. Imagine that the tree is covered with ten christmas lights. If the whole tree is in frame, then ten christmas tree lights worth of light is making it to the film. If you zoom in to show only light, then one tenth as much light is making it to the film. Just because that light looks bigger doesn’t mean that it gets any brighter.
This brings us to the final issue I wanted to talk about: exposure. Exposure means how much light makes it to the film. Exposing film is a chemical reaction, and a specific amount of light is required to make the reaction work. Too much light will make the picture look washed out, or “over exposed”. Too little light will make the picture dark, or “under exposed”. A pinhole camera has four ways to adjust exposure. You can use a shorter focal length to get more light, but at the cost making distant objects look tiny (as discussed above). You can expose the film for a longer length of time (it is not uncommon for pinhole cameras to have exposures lasting minutes or even hours). Long exposures make it hard to take pictures of anything that moves, however. (Early cameras were really little better than pinhole cameras, and took several minutes to expose. This is why pictures from that time are so serious — it is not possible to hold a smile for several minutes without moving, so people held a relaxed pose that they could stay in for several minutes.) You can put a filter in front of the pinhole to reduce the amount of light getting in. You can also alter the chemistry of the film (this is called the ISO of the film) to change how reactive it is to light.
The long exposure time of a pinhole camera is the primary reason that people invented lenses. I’ll save a discussion of lenses for another entry, however.