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ADS1248_minimal.py
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ADS1248_minimal.py
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#!/usr/bin/python
# -*- coding: utf-8 -*-
#import the library
from Adafruit_BBIO.SPI import SPI
import Adafruit_BBIO.GPIO as GPIO
import time
class ADS1248:
MUX0 = 0x00
MUX1 = 0x02
VBIAS = 0x01
SYS0 = 0x03
OFC0 = 0x04
OFC1 = 0x05
OFC2 = 0x06
FSC0 = 0x07
FSC1 = 0x08
FSC2 = 0x09
IDAC0 = 0x0a
IDAC1 = 0x0b
GPIOCFG = 0x0c
GPIODIR = 0x0d
GPIODAT = 0x0e
NOP = 0xff
WREG = 0x40
RREG = 0x20
RDATA = 0x12
# custom settings
STARTPIN = "P9_15"
def RegWrite(reg,val):
spi.xfer2([ADS1248.WREG+(reg & 0xF),0x00,val]);
return False
def RegRead(reg):
spi.xfer2([ADS1248.RREG+(reg & 0xF),00]);
r = spi.xfer2([0x00]); # dummy
return r
def ReadADC():
spi.writebytes([ADS1248.RDATA]) # RDATA (read data once, page 49)
a=spi.readbytes(3)
spi.writebytes([ADS1248.NOP]) # sending NOP
return a
def ADCinit():
RegWrite(ADS1248.MUX0, 0b00000001); # MUX0: Pos. input: AIN0, Neg. input: AIN1 (Burnout current source off)
RegWrite(ADS1248.MUX1, 0b00100000); # MUX1: REF0, normal operation
RegWrite(ADS1248.SYS0, 0b00000000); # SYS0: PGA Gain = 1, 5 SPS
RegWrite(ADS1248.IDAC0,0b00000000); # IDAC0: off
RegWrite(ADS1248.IDAC1,0b11001100); # IDAC1: n.c.
RegWrite(ADS1248.VBIAS,0b00000000); # VBIAS: BIAS voltage disabled
RegWrite(ADS1248.OFC0, 0b00000000); # OFC0: 0 => reset offset calibration
RegWrite(ADS1248.OFC1, 0b00000000); # OFC1: 0 => reset offset calibration
RegWrite(ADS1248.OFC2, 0b00000000); # OFC2: 0 => reset offset calibration
RegWrite(ADS1248.GPIOCFG, 0b00000000); # GPIOCFG: all used as analog inputs
RegWrite(ADS1248.GPIODIR, 0b00000000); # GPIODIR: -
RegWrite(ADS1248.GPIODAT, 0b00000000); # GPIODAT: -
spi = SPI(0,0) #/dev/spidev1.0
spi.msh=10000 # SPI clock set to 100 kHz
spi.bpw = 8 # bits/word
spi.threewire = False
spi.lsbfirst = False
spi.mode = 1
spi.cshigh = False # ADS1248 chip select (active low)
spi.open(0,0)
GPIO.setup("P9_14", GPIO.OUT)
# drive START high to start conversion
GPIO.setup(ADS1248.STARTPIN, GPIO.OUT)
GPIO.output(ADS1248.STARTPIN,GPIO.HIGH)
time.sleep(0.02)
ADCinit()
while True:
GPIO.output("P9_14",GPIO.HIGH)
a=ReadADC()
V=(a[0]<<16)+(a[1]<<8)+a[2]
print ("Integer reading: %d"%(V))
volts=1.0*V/(pow(2,23)-1)*3.37
print ("U = %.3f V"%(volts))
T=volts*100-273.15;
print ("T = %.2f °C"%(T))
GPIO.output("P9_14",GPIO.LOW)
time.sleep(1)