View source for Magnetometer PICAXE 20M2 program

===PICAXE Program===
This program works with the circuit described in [[Magnetometer]], when programmed on a [http://picaxe.com PICAXE] 20M2.
 ;2014 Shawn Reeves
 ;TEST RESULTS:
 ; Power consumption:6mA at 5V, i.e. 30mW
 ; ADC readings:163 to 870, zero at 514
 ; Not absolutely linear—Use lookup table for accuracy.
 
 ;Power with a 5V DC supply. Use either USB, phone charger, or 9V battery via voltage regulator.
 #picaxe 20m2
 
 ;Choose which output(s) to use:
 #define useLCD
 #define useSerial
 
 symbol adcPin = C.7	;20M2 pin 3 to SS49 pin 3
 symbol dataOut = B.3 ;20M2 pin 15 to DOGM pin 28
 symbol SCK = B.2 ;20M2 pin 16 to DOGM pin 29
 symbol CSB = B.6 ;20M2 pin 12 to DOGM pin 38
 symbol RS = B.4 ;20M2 pin 14 to DOGM pin 39
 ;assign bit memory first
 symbol negabit = bit0	;all PICAXE maths are positive integers, so we use this bit to signify negative
 symbol overflowbit = bit1
 ;assign byte memory next, avoiding conflicts with above (divide above highest by 8, round down, add one)
 symbol ones = b1;these will hold ASCII values for each digit
 symbol tens = b2
 symbol hundreds = b3
 symbol thousands = b4
 symbol tenthousands = b5
 symbol counter = b6
 symbol byteOut = b7
 ;assign word memory next, avoiding conflicts with above (divide above highest by two, round down, add one)
 symbol reading = w4
 symbol Gauss = w5
 symbol clearCommand = 1
 symbol homeCommand = 2
 
 ;This routine should initialize the Electronic Assembly DOG-ME-081 8 character LCD display
 ;use symbol command to assign CSB, RS, dataOut, and SCK to out pins
 ;assign a byte variable to byteOut and shiftCounter
 initDOG:
 high CSB ;in case spurious signals were received during powerup
 low SCK;prepare clock to work on rise
 low CSB;select chip
 low RS;sending commands, not data
 ;The following lines from Electronic Assembly's data sheet, with cursor mode altered.
 ;One might repeat the following command many times to get the attention of the ST7032 driver
 byteOut = %00110000 ;Function Set, 1 line, instruction table 0
 gosub shiftout_MSBFirst
 pauseus 27;recommended by ST7032 datasheet
 
 byteOut = %00110001 ;Function Set, 1 line, instruction table 1
 gosub shiftout_MSBFirst
 pauseus 27;recommended by ST7032 datasheet
 
 byteOut = %00110001 ;Function Set, 1 line, instruction table 1, repeat request recommended by ST7032 datasheet
 gosub shiftout_MSBFirst
 pauseus 27;recommended by ST7032 datasheet
 
 byteOut = %00011100 ;Bias 1/4, 1 line LCD
 gosub shiftout_MSBFirst
 pauseus 27;recommended by ST7032 datasheet
 
 byteOut = %01010001 ;Booster off, set contrast C5, C4
 gosub shiftout_MSBFirst
 pauseus 27;recommended by ST7032 datasheet
 
 byteOut = %01101010 ;set voltage follower on, gain 2/7
 gosub shiftout_MSBFirst
 pause 200;recommended by ST7032 datasheet
 
 byteOut = %01110100 ;set contrast C3, C2, C1
 gosub shiftout_MSBFirst
 pauseus 27;recommended by ST7032 datasheet
 
 byteOut = %00001100 ;display on, cursor off, blink cursor position
 gosub shiftout_MSBFirst
 pauseus 27;recommended by ST7032 datasheet
 
 byteOut = %00000001 ;clear display, home cursor
 gosub shiftout_MSBFirst
 pauseus 2
 
 byteOut = %00000110 ;entry from right to left (or opposite?), no scrolling.
 gosub shiftout_MSBFirst
 high RS;switch to data mode
 
 main:
 
 readHallSensor:
 readadc10 adcPin, reading 	;get a 10-bit ADC into a word
 
 convertToGauss:
 ;we have a number from 0 to 1023, representing voltage from 0 to 5V (or VCC)
 ;The SS49E Hall Sensor, at room temp, will output 0.8V at -1000 Gauss to 4V for 1000 Gauss, with zero at 2.5V
 ;We use a rough linear interpolation rather than a lookup table or polynomial curve
 ;According to measurements, the output goes from 163 to 871, a range we assume to represent -1000 to 1000 Gauss
 ;So, we multiply by the fraction 2000/708 to get Gauss from the adc reading.
 ;To make sure we don't go over 65535, the limit on our 16 bit positive integer math, we reduce the fraction to 175/62:
 ;;Maximum reading = 354*175 = 61950 < 65535
 
 negabit=0
 overflowbit = 0
 if reading > 870 then
 	overflowbit = 1
 elseif reading > 516 then
 	reading = reading-516
 	Gauss=reading*175/62
 elseif reading = 516 then
 	Gauss = 0
 elseif reading > 163 then
 	reading = 516-reading
 	Gauss = reading*175/62
 	negabit = 1
 else
 	overflowbit = 1
 	negabit = 1
 endif
 displayDigits:
 
 #ifdef useSerial
 	if negabit = 1 then
 		sertxd ("-")
 	endif
 	if overflowbit = 1 then
 		sertxd ("out of range",13,10)
 	else
 		sertxd (#Gauss," Gauss",13,10)	;baud 4800 8N1
 	endif
 #endif
 
 #ifdef useLCD
 ;split the result into digits
 bintoascii Gauss, tenthousands, thousands, hundreds, tens, ones;Convert to digits and add 48 to each.
 ;We use an Electronic Assembly (Germany) DOGM081W-A, with 8 digits and an ST7036 controller capable of SPI comm.
 low RS	;for outputting command
 byteOut = clearCommand; alternatively set DRAM address to beginning of display. This may take too long:maybe we just go home and overwrite?
 gosub shiftout_MSBFirst
 pause 2	;clear takes between 1 and 2 ms to execute.
 high RS	;for outputting data
 if negabit = 1 then
 	byteOut =  %00101101	;code for negative sign
 	gosub shiftout_MSBFirst
 endif
 if overflowbit = 1 then
 	if negabit = 0 then
 		byteOut = "o";ascii byte for 'o'
 		gosub shiftout_MSBFirst
 		byteOut = "v"
 		gosub shiftout_MSBFirst
 		byteOut = "e"
 		gosub shiftout_MSBFirst
 		byteOut = "r"
 		gosub shiftout_MSBFirst
 	else
 		byteOut = "u"
 		gosub shiftout_MSBFirst
 		byteOut = "n"
 		gosub shiftout_MSBFirst
 		byteOut = "d"
 		gosub shiftout_MSBFirst
 		byteOut = "e"
 		gosub shiftout_MSBFirst
 		byteOut = "r"
 		gosub shiftout_MSBFirst
 	endif
 else
 	byteOut =  thousands
 	gosub shiftout_MSBFirst
 	byteOut =  hundreds
 	gosub shiftout_MSBFirst
 	byteOut =  tens
 	gosub shiftout_MSBFirst
 	byteOut =  ones
 	gosub shiftout_MSBFirst
 endif
 #endif
 
 pause 490	;wait half a second, minus a bit to account for display routine
 
 goto main	;do it all again
 
 shiftout_MSBFirst:
 for counter = 1 to 8
 	if byteOut > 127 then ;MSb must be 1
 		high dataOut
 	else
 		low dataOut
 	endif
 	;data must be set at least 10ns before clock rises. If overclocking, uncomment the following line:
 	;pauseus 1
 	high SCK
 	byteOut = byteOut * 2	;Shift the value so we mask the next bit
 	;data must remain set at least 150ns after clock rises.
 	pauseus 1	;wait 10 microseconds.
 	low SCK
 next counter
 return

[[Category:Electronics]]