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ADS1256.py
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ADS1256.py
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# Python module for ADS1256
from libbcm2835._bcm2835 import *
import numpy as np
import time
# define constants
# gain channel
ADS1256_GAIN_E = {'ADS1256_GAIN_1' : 0, # GAIN 1
'ADS1256_GAIN_2' : 1, # GAIN 2
'ADS1256_GAIN_4' : 2, # GAIN 4
'ADS1256_GAIN_8' : 3, # GAIN 8
'ADS1256_GAIN_16' : 4,# GAIN 16
'ADS1256_GAIN_32' : 5,# GAIN 32
'ADS1256_GAIN_64' : 6,# GAIN 64
}
# data rate
ADS1256_DRATE_E = {'ADS1256_30000SPS' : 0xF0, # reset the default values
'ADS1256_15000SPS' : 0xE0,
'ADS1256_7500SPS' : 0xD0,
'ADS1256_3750SPS' : 0xC0,
'ADS1256_2000SPS' : 0xB0,
'ADS1256_1000SPS' : 0xA1,
'ADS1256_500SPS' : 0x92,
'ADS1256_100SPS' : 0x82,
'ADS1256_60SPS' : 0x72,
'ADS1256_50SPS' : 0x63,
'ADS1256_30SPS' : 0x53,
'ADS1256_25SPS' : 0x43,
'ADS1256_15SPS' : 0x33,
'ADS1256_10SPS' : 0x20,
'ADS1256_5SPS' : 0x13,
'ADS1256_2d5SPS' : 0x03
}
# registration definition
REG_E = {'REG_STATUS' : 0, # x1H
'REG_MUX' : 1, # 01H
'REG_ADCON' : 2, # 20H
'REG_DRATE' : 3, # F0H
'REG_IO' : 4, # E0H
'REG_OFC0' : 5, # xxH
'REG_OFC1' : 6, # xxH
'REG_OFC2' : 7, # xxH
'REG_FSC0' : 8, # xxH
'REG_FSC1' : 9, # xxH
'REG_FSC2' : 10, # xxH
}
# command definition
CMD = {'CMD_WAKEUP' : 0x00, # Completes SYNC and Exits Standby Mode 0000 0000 (00h)
'CMD_RDATA' : 0x01, # Read Data 0000 0001 (01h)
'CMD_RDATAC' : 0x03, # Read Data Continuously 0000 0011 (03h)
'CMD_SDATAC' : 0x0F, # Stop Read Data Continuously 0000 1111 (0Fh)
'CMD_RREG' : 0x10, # Read from REG rrr 0001 rrrr (1xh)
'CMD_WREG' : 0x50, # Write to REG rrr 0101 rrrr (5xh)
'CMD_SELFCAL' : 0xF0, # Offset and Gain Self-Calibration 1111 0000 (F0h)
'CMD_SELFOCAL' : 0xF1, # Offset Self-Calibration 1111 0001 (F1h)
'CMD_SELFGCAL' : 0xF2, # Gain Self-Calibration 1111 0010 (F2h)
'CMD_SYSOCAL' : 0xF3, # System Offset Calibration 1111 0011 (F3h)
'CMD_SYSGCAL' : 0xF4, # System Gain Calibration 1111 0100 (F4h)
'CMD_SYNC' : 0xFC, # Synchronize the A/D Conversion 1111 1100 (FCh)
'CMD_STANDBY' : 0xFD, # Begin Standby Mode 1111 1101 (FDh)
'CMD_RESET' : 0xFE, # Reset to Power-Up Values 1111 1110 (FEh)
}
# ADS1256 Python Module
class ADS1256:
def __init__(self, ch_num=0, gain='ADS1256_GAIN_1', rate='ADS1256_100SPS'):
'''initialization and constants registration'''
# data storage
if ADS1256_GAIN_E.has_key(gain):
self.Gain = ADS1256_GAIN_E[gain]
else:
self.Gain = ADS1256_GAIN_E['ADS1256_GAIN_1'] # GAIN 1
if ADS1256_DRATE_E.has_key(rate):
self.DataRate = ADS1256_DRATE_E[rate]
else:
self.DataRate = ADS1256_DRATE_E['ADS1256_100SPS'] # DATA output speed
self.AdcNow = [0, 0, 0, 0, 0, 0, 0, 0] # ADC Conversion value
self.Channel = ch_num # The current channel
self.ScanMode = 0 # Scanning mode_ 0 : Single-ended input 8 channel; 1 : Differential input 4 channel
# define constants for future usage
self.DRDY = RPI_GPIO_P1_11 #P0
self.RST = RPI_GPIO_P1_12 #P1
self.SPICS = RPI_GPIO_P1_15 #P3
# adc chip initialization
if not bcm2835_init():
return
self.chipInit()
self.ADS1256_CfgADC(self.Gain, self.DataRate)
self.ADS1256_StartScan(0, self.Channel)
def chipInit(self):
'''configure the chip before data transmission'''
bcm2835_spi_begin()
# default setting for ADS1256
#bcm2835_spi_setBitOrder(BCM2835_SPI_BIT_ORDER_LSBFIRST ); #The default
#bcm2835_spi_setDataMode(BCM2835_SPI_MODE1); #The default
#bcm2835_spi_setClockDivider(BCM2835_SPI_CLOCK_DIVIDER_1024);#The default
# default setting from motor control
bcm2835_spi_setBitOrder(BCM2835_SPI_BIT_ORDER_MSBFIRST); # Edited follow Arduino command
# Set Register x00 to set bit order
bcm2835_spi_setDataMode(BCM2835_SPI_MODE3); # Edited follow Arduino Command
bcm2835_spi_setClockDivider(BCM2835_SPI_CLOCK_DIVIDER_4096);
bcm2835_gpio_fsel(self.SPICS, BCM2835_GPIO_FSEL_OUTP);
bcm2835_gpio_write(self.SPICS, HIGH);
bcm2835_gpio_fsel(self.DRDY, BCM2835_GPIO_FSEL_INPT);
bcm2835_gpio_set_pud(self.DRDY, BCM2835_GPIO_PUD_UP);
def set_CS_High(self):
'''set CS to HIGH'''
bcm2835_gpio_write(self.SPICS,HIGH)
def set_CS_Low(self):
'''set CS to LOW'''
bcm2835_gpio_write(self.SPICS,LOW)
def dataReady_is_Low(self):
'''check if data is ready'''
return (bcm2835_gpio_lev(self.DRDY) == 0)
def set_RST_High(self):
'''set RST to HIGH'''
self.bcm2835_gpio_write(self.RST,HIGH)
def set_RST_Low(self):
'''set RST to LOW'''
self.bcm2835_gpio_write(self.RST,LOW)
def bsp_DelayUS(self, micros):
'''delay for microseconds before procede'''
bcm2835_delayMicroseconds (micros)
def bsp_InitADS1256(self):
'''SOFT SPI?'''
print "SOFT SPI? NOT IMPLEMENTED YET"
def ADS1256_StartScan(self, _ucScanMode, _chnum):
'''Configuration DRDY PIN for external interrupt is triggered'''
self.ScanMode =_ucScanMode
self.Channel = _chnum
self.ADS1256_SetChannel(self.Channel)
self.AdcNow = [0, 0, 0, 0, 0, 0, 0, 0] # reset
#print self.AdcNow
def ADS1256_Send8Bit(self, _data):
'''SPI bus to send 8 bit data'''
self.bsp_DelayUS(2)
bcm2835_spi_transfer(_data)
def ADS1256_CfgADC(self, _gain, _drate):
'''The configuration parameters of ADC, gain and data rate'''
self.Gain = _gain
self.DataRate = _drate
self.ADS1256_WaitDRDY()
# Storage ads1256 register configuration parameters
buf = [0x00, 0x00, 0x00, 0x00];
### Status register define
# Bits 7-4 ID3, ID2, ID1, ID0 Factory Programmed Identification Bits (Read Only)
#
# Bit 3 ORDER: Data Output Bit Order
# 0 = Most Significant Bit First (default)
# 1 = Least Significant Bit First
# Input data is always shifted in most significant byte and bit first. Output data is always shifted out most significant
# byte first. The ORDER bit only controls the bit order of the output data within the byte.
#
# Bit 2 ACAL : Auto-Calibration
# 0 = Auto-Calibration Disabled (default)
# 1 = Auto-Calibration Enabled
# When Auto-Calibration is enabled, self-calibration begins at the completion of the WREG command that changes
# the PGA (bits 0-2 of ADCON register), DR (bits 7-0 in the DRATE register) or BUFEN (bit 1 in the STATUS register)
# values.
#
# Bit 1 BUFEN: Analog Input Buffer Enable
# 0 = Buffer Disabled (default)
# 1 = Buffer Enabled
#
# Bit 0 DRDY : Data Ready (Read Only)
# This bit duplicates the state of the DRDY pin.
#
# ACAL=1 enable calibration
###
# //buf[0] = (0 << 3) | (1 << 2) | (1 << 1);//enable the internal buffer
buf[0] = (0 << 3) | (1 << 2) | (0 << 1); # 0000 0100: MSBF, Auto-cal, Buffer disabled, Data Ready
# MUX: Input multiplexer Control register (Address 01h)
# Bits 7-4: Positive Input Channel (0-7 = AIN0-7, 1xxx = AINCOM)
# Bits 3-0: Negative Input Channel (0-7 = AIN0-7, 1xxx = AINCOM)
buf[1] = 0x08 # Positive Input Channel: AIN0, Negative Input Channel: AINCOM
# /* ADCON: A/D Control Register (Address 02h)
# Bit 7 Reserved, always 0 (Read Only)
# Bits 6-5 CLK1, CLK0 : D0/CLKOUT Clock Out Rate Setting
# 00 = Clock Out OFF
# 01 = Clock Out Frequency = fCLKIN (default)
# 10 = Clock Out Frequency = fCLKIN/2
# 11 = Clock Out Frequency = fCLKIN/4
# When not using CLKOUT, it is recommended that it be turned off. These bits can only be reset using the RESET pin.
#
# Bits 4-3 SDCS1, SCDS0: Sensor Detect Current Sources
# 00 = Sensor Detect OFF (default)
# 01 = Sensor Detect Current = 0.5 A
# 10 = Sensor Detect Current = 2 A
# 11 = Sensor Detect Current = 10 A
# The Sensor Detect Current Sources can be activated to verify the integrity of an external sensor supplying a signal to the
# ADS1255/6. A shorted sensor produces a very small signal while an open-circuit sensor produces a very large signal.
#
# Bits 2-0 PGA2, PGA1, PGA0: Programmable Gain Amplifier Setting
# 000 = 1 (default)
# 001 = 2
# 010 = 4
# 011 = 8
# 100 = 16
# 101 = 32
# 110 = 64
# 111 = 64
# */
buf[2] = (0 << 5) | (0 << 3) | (_gain << 0) # Clock out off, Sensor detect off, gain = 1
#//ADS1256_WriteReg(REG_ADCON, (0 << 5) | (0 << 2) | (GAIN_1 << 1)); /*choose 1: gain 1 ;input 5V/
buf[3] = self.DataRate #ADS1256_DRATE_E[_drate]
self.set_CS_Low()
self.ADS1256_Send8Bit(CMD['CMD_WREG'] | 0) # Write register, starting with register address 0
self.ADS1256_Send8Bit(0x03); # number of bytes to be sent: 4 (writing 4 registers), set the number = 4 - 1
self.ADS1256_Send8Bit(buf[0]) # Set the status register
self.ADS1256_Send8Bit(buf[1]) # Set the input channel parameters
self.ADS1256_Send8Bit(buf[2]) # Set the ADCON control register,gain
self.ADS1256_Send8Bit(buf[3]) # Set the output rate
self.set_CS_High() # SPI cs = 1
self.bsp_DelayUS(50)
#print hex(buf[0]), hex(buf[1]), hex(buf[2]), hex(buf[3])
def ADS1256_DelayDATA(self):
'''Delay from last SCLK edge for DIN to first SCLK rising edge for DOUT: RDATA, RDATAC,RREG Commands. Minimum 50 CLK = 50 * 0.13uS = 6.5uS'''
self.bsp_DelayUS(10) # The minimum time delay 6.5us
def ADS1256_Recive8Bit(self):
'''Receive 8 bit'''
return bcm2835_spi_transfer(0xff)
def ADS1256_WriteReg(self, _RegID, _RegValue):
'''Write the corresponding register'''
self.set_CS_Low()
self.ADS1256_Send8Bit(CMD['CMD_WREG'] | _RegID) # Write command register
self.ADS1256_Send8Bit(0x00) # Write the register number
self.ADS1256_Send8Bit(_RegValue) # send register value
self.set_CS_High()
def ADS1256_ReadReg(self, _RegID):
'''Read the corresponding register'''
self.set_CS_Low()
self.ADS1256_Send8Bit(CMD['CMD_RREG'] | _RegID)
self.ADS1256_Send8Bit(0x00)
self.ADS1256_DelayDATA()
read = self.ADS1256_Recive8Bit()
self.set_CS_High()
return read
def ADS1256_WriteCmd(self, _cmd):
'''Sending a single byte order'''
self.set_CS_Low()
self.ADS1256_Send8Bit(_cmd)
self.set_CS_High()
def ADS1256_ReadChipID(self):
'''Read the chip ID'''
self.ADS1256_WaitDRDY();
chipID = self.ADS1256_ReadReg(REG_E['REG_STATUS'])
return (chipID >> 4)
def ADS1256_SetChannel(self, _ch):
'''Configuration channel number'''
# /*
# Bits 7-4 PSEL3, PSEL2, PSEL1, PSEL0: Positive Input Channel (AINP) Select
# 0000 = AIN0 (default)
# 0001 = AIN1
# 0010 = AIN2 (ADS1256 only)
# 0011 = AIN3 (ADS1256 only)
# 0100 = AIN4 (ADS1256 only)
# 0101 = AIN5 (ADS1256 only)
# 0110 = AIN6 (ADS1256 only)
# 0111 = AIN7 (ADS1256 only)
# 1xxx = AINCOM (when PSEL3 = 1, PSEL2, PSEL1, PSEL0 are dont care)
#
# NOTE: When using an ADS1255 make sure to only select the available inputs.
#
# Bits 3-0 NSEL3, NSEL2, NSEL1, NSEL0: Negative Input Channel (AINN)Select
# 0000 = AIN0
# 0001 = AIN1 (default)
# 0010 = AIN2 (ADS1256 only)
# 0011 = AIN3 (ADS1256 only)
# 0100 = AIN4 (ADS1256 only)
# 0101 = AIN5 (ADS1256 only)
# 0110 = AIN6 (ADS1256 only)
# 0111 = AIN7 (ADS1256 only)
# 1xxx = AINCOM (when NSEL3 = 1, NSEL2, NSEL1, NSEL0 are dont care)
# */
if (_ch > 7):
return
self.ADS1256_WriteReg(REG_E['REG_MUX'], (_ch << 4) | (1 << 3)) # Bit3 = 1, AINN connection AINCOM
self.Channel = _ch
def ADS1256_SetDiffChannel(self, _ch):
'''The configuration difference channel'''
## Bits 7-4 PSEL3, PSEL2, PSEL1, PSEL0: Positive Input Channel (AINP) Select
## 0000 = AIN0 (default)
## 0001 = AIN1
## 0010 = AIN2 (ADS1256 only)
## 0011 = AIN3 (ADS1256 only)
## 0100 = AIN4 (ADS1256 only)
## 0101 = AIN5 (ADS1256 only)
## 0110 = AIN6 (ADS1256 only)
## 0111 = AIN7 (ADS1256 only)
## 1xxx = AINCOM (when PSEL3 = 1, PSEL2, PSEL1, PSEL0 are dont't care)
##
## NOTE: When using an ADS1255 make sure to only select the available inputs.
##
## Bits 3-0 NSEL3, NSEL2, NSEL1, NSEL0: Negative Input Channel (AINN)Select
## 0000 = AIN0
## 0001 = AIN1 (default)
## 0010 = AIN2 (ADS1256 only)
## 0011 = AIN3 (ADS1256 only)
## 0100 = AIN4 (ADS1256 only)
## 0101 = AIN5 (ADS1256 only)
## 0110 = AIN6 (ADS1256 only)
## 0111 = AIN7 (ADS1256 only)
## 1xxx = AINCOM (when NSEL3 = 1, NSEL2, NSEL1, NSEL0 are don't care)
if (_ch == 0):
self.ADS1256_WriteReg(REG_E['REG_MUX'], (0 << 4) | 1); # /* DiffChannel AIN0 - AIN1 */
elif (_ch == 1):
self.ADS1256_WriteReg(REG_E['REG_MUX'], (2 << 4) | 3); # /*DiffChannel AIN2 - AIN3 */
elif (_ch == 2):
self.ADS1256_WriteReg(REG_E['REG_MUX'], (4 << 4) | 5); # /*DiffChannel AIN4 - AIN5 */
elif (_ch == 3):
self.ADS1256_WriteReg(REG_E['REG_MUX'], (6 << 4) | 7); # /*DiffChannel AIN6 - AIN7 */
if (_ch in range(4)):
self.Channel = _ch
def ADS1256_WaitDRDY(self):
'''delay time wait for automatic calibration'''
for i in range(400000):
if (self.dataReady_is_Low()):
break
if ( i >= 400000):
print "ADS1256_WaitDRDY() Time Out ...\r\n"
def ADS1256_ReadData(self):
'''read ADC value'''
read = 0
buf = [0x00, 0x00, 0x00]
self.set_CS_Low()
self.ADS1256_Send8Bit(CMD['CMD_RDATA']); # read ADC command
self.ADS1256_DelayDATA(); # delay time
# Read the sample results 24-bit
buf[0] = self.ADS1256_Recive8Bit();
buf[1] = self.ADS1256_Recive8Bit();
buf[2] = self.ADS1256_Recive8Bit();
read = (np.int32(buf[0] << 16)) & 0x00FF0000
read = read | (buf[1] << 8) # Pay attention to It is wrong read |= (buf[1] << 8) */
read = read | buf[2]
self.set_CS_High()
# Extend a signed number
if (read & 0x800000):
read = read | 0xFF000000
return np.int32(read)
def ADS1256_GetAdc(self, _ch):
'''read stored ADC value'''
if (_ch > 7):
return 0
return self.AdcNow[_ch]
## def ADS1256_ScanAndReadChannel(self, _ch=-1):
## '''scan and readout'''
## if (_ch > 7):
## return None
## self.ADS1256_Scan()
## if (True):#(self.ADS1256_Scan() == 1):
## if (_ch == -1): # reading all channels
## readout = [self.ADS1256_GetAdc(i) for i in range(8)]
## else:
## readout = [self.ADS1256_GetAdc(_ch)]
## return [self.Data_To_Volt(val) for val in readout]
## else:
## return None
def ADS1256_OneShot(self, _ch):
'''one shot read channel'''
if ( _ch != self.Channel ):
self.ADS1256_SetChannel(self.Channel)
self.bsp_DelayUS(5)
self.ADS1256_WriteCmd(CMD['CMD_SYNC'])
self.bsp_DelayUS(5)
self.ADS1256_WriteCmd(CMD['CMD_WAKEUP']);
self.bsp_DelayUS(25)
self.AdcNow[self.Channel] = self.ADS1256_ReadData()
return self.Data_To_Volt(self.AdcNow[self.Channel])
def ADS1256_ISR(self):
'''Collection procedures'''
if (self.ScanMode == 0): # 0 Single-ended input 8 channel
self.ADS1256_SetChannel(self.Channel) # Switch channel mode
self.bsp_DelayUS(5)
self.ADS1256_WriteCmd(CMD['CMD_SYNC'])
self.bsp_DelayUS(5)
self.ADS1256_WriteCmd(CMD['CMD_WAKEUP']);
self.bsp_DelayUS(25)
if (self.Channel == 0):
self.AdcNow[self.Channel] = self.ADS1256_ReadData()
else:
self.AdcNow[self.Channel] = self.ADS1256_ReadData()
self.Channel = self.Channel + 1
if (self.Channel >= 8):
self.Channel = 0
else: # 1 Differential input 4 channel
self.ADS1256_SetDiffChannel(self.Channel) # change DiffChannel
self.bsp_DelayUS(5)
self.ADS1256_WriteCmd(CMD['CMD_SYNC'])
self.bsp_DelayUS(5)
self.ADS1256_WriteCmd(CMD['CMD_WAKEUP'])
self.bsp_DelayUS(25)
if (self.Channel == 0):
self.AdcNow[3] = self.ADS1256_ReadData()
else:
self.AdcNow[self.Channel-1] = self.ADS1256_ReadData()
self.Channel = self.Channel + 1
if (self.Channel >= 4):
self.Channel = 0
def ADS1256_Scan(self):
'''Scan function'''
if (self.dataReady_is_Low()): # Data is ready, collect data
self.ADS1256_ISR()
return 1
return 0
def Write_DAC8552(self, channel, Data):
'''DAC send data'''
print "DAC send data: NOT IMPLEMENTED YET"
def Voltage_Convert(self, Vref, voltage):
'''Voltage value conversion function. Vref : The reference voltage 3.3V or 5V
voltage : output DAC value'''
return np.int16(65536 * voltage / Vref)
def Data_To_Volt(self, val):
'''Convert 24 bits to voltage'''
return (val * 100) / 167 / 1000000.0
def main_ADS1256():
'''Module testing helper function'''
print "TESTING STARTS!"
if not bcm2835_init():
return
try:
ch_num = 0
adc = ADS1256(ch_num)
readout_val = [0,0,0,0,0,0,0,0]#-1.0
volt_val = [0,0,0,0,0,0,0,0] #-2.0
while True:
#print adc.ADS1256_ScanAndReadChannel(1)
adc.ADS1256_OneShot(0)
print [adc.Data_To_Volt(val) for val in adc.AdcNow]
## if (adc.ADS1256_Scan() == 1):
## for i in [1]:#range(8):
## readout_val[i] = adc.ADS1256_GetAdc(i)
## volt_val[i] = (readout_val[i] * 100) / 167 / 1000000.0
## #print "readout_val = ", readout_val
## print " volt_val = ", volt_val
## else:
## print "NO scan performed!"
adc.bsp_DelayUS(10000)#(100000) # limited sampling rate
finally:
bcm2835_spi_end()
bcm2835_close()
print "TESTING ENDS"
if __name__ == '__main__':
main_ADS1256()