#!/usr/bin/python """ ================================================ ABElectronics ADC Pi V2 8-Channel ADC Version 1.0 Created 09/05/2014 Version 1.1 16/11/2014 updated code and functions to PEP8 format Requires python smbus to be installed ================================================ """ class ADCPi: # internal variables __address = 0x68 # default address for adc 1 on adc pi and delta-sigma pi __address2 = 0x69 # default address for adc 2 on adc pi and delta-sigma pi __config1 = 0x9C # PGAx1, 18 bit, continuous conversion, channel 1 __currentchannel1 = 1 # channel variable for adc 1 __config2 = 0x9C # PGAx1, 18 bit, continuous-shot conversion, channel 1 __currentchannel2 = 1 # channel variable for adc2 __bitrate = 18 # current bitrate __conversionmode = 1 # Conversion Mode __pga = float(0.5) # current pga setting __lsb = float(0.0000078125) # default lsb value for 18 bit # create byte array and fill with initial values to define size __adcreading = bytearray() __adcreading.append(0x00) __adcreading.append(0x00) __adcreading.append(0x00) __adcreading.append(0x00) global _bus # local methods def __updatebyte(self, byte, bit, value): # internal method for setting the value of a single bit within a # byte if value == 0: return byte & ~(1 << bit) elif value == 1: return byte | (1 << bit) def __checkbit(self, byte, bit): # internal method for reading the value of a single bit within a # byte bitval = ((byte & (1 << bit)) != 0) if (bitval == 1): return True else: return False def __twos_comp(self, val, bits): if((val & (1 << (bits - 1))) != 0): val = val - (1 << bits) return val def __setchannel(self, channel): # internal method for updating the config to the selected channel if channel < 5: if channel != self.__currentchannel1: if channel == 1: self.__config1 = self.__updatebyte(self.__config1, 5, 0) self.__config1 = self.__updatebyte(self.__config1, 6, 0) self.__currentchannel1 = 1 if channel == 2: self.__config1 = self.__updatebyte(self.__config1, 5, 1) self.__config1 = self.__updatebyte(self.__config1, 6, 0) self.__currentchannel1 = 2 if channel == 3: self.__config1 = self.__updatebyte(self.__config1, 5, 0) self.__config1 = self.__updatebyte(self.__config1, 6, 1) self.__currentchannel1 = 3 if channel == 4: self.__config1 = self.__updatebyte(self.__config1, 5, 1) self.__config1 = self.__updatebyte(self.__config1, 6, 1) self.__currentchannel1 = 4 else: if channel != self.__currentchannel2: if channel == 5: self.__config2 = self.__updatebyte(self.__config2, 5, 0) self.__config2 = self.__updatebyte(self.__config2, 6, 0) self.__currentchannel2 = 5 if channel == 6: self.__config2 = self.__updatebyte(self.__config2, 5, 1) self.__config2 = self.__updatebyte(self.__config2, 6, 0) self.__currentchannel2 = 6 if channel == 7: self.__config2 = self.__updatebyte(self.__config2, 5, 0) self.__config2 = self.__updatebyte(self.__config2, 6, 1) self.__currentchannel2 = 7 if channel == 8: self.__config2 = self.__updatebyte(self.__config2, 5, 1) self.__config2 = self.__updatebyte(self.__config2, 6, 1) self.__currentchannel2 = 8 return # init object with i2caddress, default is 0x68, 0x69 for ADCoPi board def __init__(self, bus, address=0x68, address2=0x69, rate=18): self._bus = bus self.__address = address self.__address2 = address2 self.set_bit_rate(rate) def read_voltage(self, channel): # returns the voltage from the selected adc channel - channels 1 to # 8 raw = self.read_raw(channel) if (self.__signbit): return float(0.0) # returned a negative voltage so return 0 else: voltage = float( (raw * (self.__lsb / self.__pga)) * 2.471) return float(voltage) def read_raw(self, channel): # reads the raw value from the selected adc channel - channels 1 to 8 h = 0 l = 0 m = 0 s = 0 # get the config and i2c address for the selected channel self.__setchannel(channel) if (channel < 5): config = self.__config1 address = self.__address else: config = self.__config2 address = self.__address2 # if the conversion mode is set to one-shot update the ready bit to 1 if (self.__conversionmode == 0): config = self.__updatebyte(config, 7, 1) self._bus.write_byte(address, config) config = self.__updatebyte(config, 7, 0) # keep reading the adc data until the conversion result is ready while True: __adcreading = self._bus.read_i2c_block_data(address, config, 4) if self.__bitrate == 18: h = __adcreading[0] m = __adcreading[1] l = __adcreading[2] s = __adcreading[3] else: h = __adcreading[0] m = __adcreading[1] s = __adcreading[2] if self.__checkbit(s, 7) == 0: break self.__signbit = False t = 0.0 # extract the returned bytes and combine in the correct order if self.__bitrate == 18: t = ((h & 0b00000011) << 16) | (m << 8) | l self.__signbit = bool(self.__checkbit(t, 17)) if self.__signbit: t = self.__updatebyte(t, 17, 0) if self.__bitrate == 16: t = (h << 8) | m self.__signbit = bool(self.__checkbit(t, 15)) if self.__signbit: t = self.__updatebyte(t, 15, 0) if self.__bitrate == 14: t = ((h & 0b00111111) << 8) | m self.__signbit = self.__checkbit(t, 13) if self.__signbit: t = self.__updatebyte(t, 13, 0) if self.__bitrate == 12: t = ((h & 0b00001111) << 8) | m self.__signbit = self.__checkbit(t, 11) if self.__signbit: t = self.__updatebyte(t, 11, 0) return t def set_pga(self, gain): """ PGA gain selection 1 = 1x 2 = 2x 4 = 4x 8 = 8x """ if gain == 1: self.__config1 = self.__updatebyte(self.__config1, 0, 0) self.__config1 = self.__updatebyte(self.__config1, 1, 0) self.__config2 = self.__updatebyte(self.__config2, 0, 0) self.__config2 = self.__updatebyte(self.__config2, 1, 0) self.__pga = 0.5 if gain == 2: self.__config1 = self.__updatebyte(self.__config1, 0, 1) self.__config1 = self.__updatebyte(self.__config1, 1, 0) self.__config2 = self.__updatebyte(self.__config2, 0, 1) self.__config2 = self.__updatebyte(self.__config2, 1, 0) self.__pga = 1 if gain == 4: self.__config1 = self.__updatebyte(self.__config1, 0, 0) self.__config1 = self.__updatebyte(self.__config1, 1, 1) self.__config2 = self.__updatebyte(self.__config2, 0, 0) self.__config2 = self.__updatebyte(self.__config2, 1, 1) self.__pga = 2 if gain == 8: self.__config1 = self.__updatebyte(self.__config1, 0, 1) self.__config1 = self.__updatebyte(self.__config1, 1, 1) self.__config2 = self.__updatebyte(self.__config2, 0, 1) self.__config2 = self.__updatebyte(self.__config2, 1, 1) self.__pga = 4 self._bus.write_byte(self.__address, self.__config1) self._bus.write_byte(self.__address2, self.__config2) return def set_bit_rate(self, rate): """ sample rate and resolution 12 = 12 bit (240SPS max) 14 = 14 bit (60SPS max) 16 = 16 bit (15SPS max) 18 = 18 bit (3.75SPS max) """ if rate == 12: self.__config1 = self.__updatebyte(self.__config1, 2, 0) self.__config1 = self.__updatebyte(self.__config1, 3, 0) self.__config2 = self.__updatebyte(self.__config2, 2, 0) self.__config2 = self.__updatebyte(self.__config2, 3, 0) self.__bitrate = 12 self.__lsb = 0.0005 if rate == 14: self.__config1 = self.__updatebyte(self.__config1, 2, 1) self.__config1 = self.__updatebyte(self.__config1, 3, 0) self.__config2 = self.__updatebyte(self.__config2, 2, 1) self.__config2 = self.__updatebyte(self.__config2, 3, 0) self.__bitrate = 14 self.__lsb = 0.000125 if rate == 16: self.__config1 = self.__updatebyte(self.__config1, 2, 0) self.__config1 = self.__updatebyte(self.__config1, 3, 1) self.__config2 = self.__updatebyte(self.__config2, 2, 0) self.__config2 = self.__updatebyte(self.__config2, 3, 1) self.__bitrate = 16 self.__lsb = 0.00003125 if rate == 18: self.__config1 = self.__updatebyte(self.__config1, 2, 1) self.__config1 = self.__updatebyte(self.__config1, 3, 1) self.__config2 = self.__updatebyte(self.__config2, 2, 1) self.__config2 = self.__updatebyte(self.__config2, 3, 1) self.__bitrate = 18 self.__lsb = 0.0000078125 self._bus.write_byte(self.__address, self.__config1) self._bus.write_byte(self.__address2, self.__config2) return def set_conversion_mode(self, mode): """ conversion mode for adc 0 = One shot conversion mode 1 = Continuous conversion mode """ if (mode == 0): self.__config1 = self.__updatebyte(self.__config1, 4, 0) self.__config2 = self.__updatebyte(self.__config2, 4, 0) self.__conversionmode = 0 if (mode == 1): self.__config1 = self.__updatebyte(self.__config1, 4, 1) self.__config2 = self.__updatebyte(self.__config2, 4, 1) self.__conversionmode = 1 #self._bus.write_byte(self.__address, self.__config1) #self._bus.write_byte(self.__address2, self.__config2) return