Fix ADC-lib to use 12Bit, Rework read_analog example + channel mapping
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jonny
parent
1fa1149170
commit
1be9545cd1
@ -7,14 +7,70 @@ import time
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# Include custom files
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# Add the parent directory to the module search path
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sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), "..")))
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from interface_board_libs.adc_mcp3208 import MCP3208
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from interface_board_pins import ADC_CHANNELS
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from interface_board_libs.adc_mcp3208 import MCP3208 # custom driver for ADC-IC
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from interface_board_pins import (
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ADC_CHANNELS,
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ADC_CHANNEL_T0__0_TO_3V3,
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ADC_CHANNEL_T1__0_TO_3V3,
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ADC_CHANNEL_T2__0_TO_5V,
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ADC_CHANNEL_T3__0_TO_5V,
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ADC_CHANNEL_T4__0_TO_12V,
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ADC_CHANNEL_T5__0_TO_12V,
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ADC_CHANNEL_T6__0_TO_20MA,
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ADC_CHANNEL_T7__0_TO_20MA,
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) # mapping of ADC channels to terminals
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# create ADC instance
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adc = MCP3208()
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# local helper function to scale the adc value to an actual voltage
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def adc2value(adc_value, max_value):
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max_adc = 4095
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return adc_value * max_value / max_adc
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while True:
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print ("==================")
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for i in range(8):
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print('ADC[{}]: {:.2f}'.format(i, adc.read(i)))
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time.sleep(0.5)
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print ("")
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# Read all available channels in a loop according to terminal order / map
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values = []
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for terminal, adc_channel in ADC_CHANNELS.items():
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value = adc.read(adc_channel)
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print(f"T{terminal}: ADC={value:04d} => U_ADC = {adc2value(value, 3.3):5.3f}V")
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# Read channels one by one using defined constants (more intuitive)
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print("-" * 40)
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value = adc.read(ADC_CHANNEL_T0__0_TO_3V3)
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print(f"Terminal 0 (0 to 3.3V): ADC={value:04d} => Terminal={adc2value(value, 3.3):4.2f}V")
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value = adc.read(ADC_CHANNEL_T1__0_TO_3V3)
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print(f"Terminal 1 (0 to 3.3V): ADC={value:04d} => Terminal={adc2value(value, 3.3):4.2f}V")
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value = adc.read(ADC_CHANNEL_T2__0_TO_5V)
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print(f"Terminal 2 (0 to 5V): ADC={value:04d} => Terminal={adc2value(value, 5):4.2f}V")
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value = adc.read(ADC_CHANNEL_T3__0_TO_5V)
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print(f"Terminal 3 (0 to 5V): ADC={value:04d} => Terminal={adc2value(value, 5):4.2f}V")
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value = adc.read(ADC_CHANNEL_T4__0_TO_12V)
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print(f"Terminal 4 (0 to 12V): ADC={value:04d} => Terminal={adc2value(value, 12):05.2f}V")
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value = adc.read(ADC_CHANNEL_T5__0_TO_12V)
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print(f"Terminal 5 (0 to 12V): ADC={value:04d} => Terminal={adc2value(value, 12):05.2f}V")
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value = adc.read(ADC_CHANNEL_T6__0_TO_20MA)
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print(f"Terminal 6 (0 to 20mA): ADC={value:04d} => Terminal={adc2value(value, 20):05.2f}mA")
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value = adc.read(ADC_CHANNEL_T7__0_TO_20MA)
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print(f"Terminal 7 (0 to 20mA): ADC={value:04d} => Terminal={adc2value(value, 20):05.2f}mA")
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print("-" * 40)
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time.sleep(1) # Delay before next read cycle
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@ -1,6 +1,9 @@
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import spidev
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import time
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DEBUG = False
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class MCP3208:
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def __init__(self, bus=0, device=0):
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# Initialize SPI bus and device
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@ -9,36 +12,55 @@ class MCP3208:
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self.spi.max_speed_hz = 1000000 # Adjust based on your needs (e.g., 1MHz)
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self.spi.mode = 0b00 # Set SPI mode (Mode 0 for MCP3208)
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def read(self, channel):
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"""
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Read the ADC value from the specified channel (0-7).
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"""
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# MCP3208 is a 12-bit SPI ADC. Communication requires sending a 3-byte command and receiving a 3-byte response.
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# The bits in the command sequence are structured as follows:
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# Command Byte (8 bits):
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# | Start (1) | Mode (1) | Channel (3) | Padding (3) |
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# The MCP3208 responds with 3 bytes:
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# - Byte 1: Contains the highest bit (bit 11) of the 12-bit ADC result.
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# - Byte 2: Contains bits 10-3 of the ADC result.
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# - Byte 3: Contains bits 2-0 of the ADC result.
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# Ensure the channel is valid (0-7)
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if channel < 0 or channel > 7:
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raise ValueError("Channel must be between 0 and 7.")
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raise ValueError(f"Channel must be between 0 and 7. (current channel={channel})")
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# MCP3208 sends a 3-byte response, which needs to be processed
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# Start with the single bit control byte, followed by the channel selection
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# MCP3208 uses 3 bits for the channel: 0-7
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# The command byte looks like this:
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# | Start | Single-ended | Channel (3 bits) | Don't Care (1 bit) |
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# Construct the command byte sequence:
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# - Start bit (1) -> 1000 0000 (0x80)
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# - Single-ended (1) -> 1100 0000 (0xC0)
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# - Channel (3 bits) shifted into position
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cmd = 0x80 # Start bit: 1000 0000
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cmd |= 0x40 # Single-ended mode: 1100 0000
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cmd |= (channel & 0x07) << 3 # Move channel number to bits 5-3
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# Construct the 3-byte command
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# Start bit (1) | Single-ended (1) | Channel (3 bits) | Don't care (1) | End (1)
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command = [1, (8 + channel) << 4, 0]
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# Send the command and receive the 3-byte response
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ret = self.spi.xfer2([cmd, 0x00, 0x00]) # Send 3 bytes, receive 3 bytes
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# Send command and receive the 3-byte result
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result = self.spi.xfer2(command)
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if DEBUG:
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print(f"result[0]: {bin(ret[0])}, result[1]: {bin(ret[1])}, result[2]: {bin(ret[2])}")
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# Combine the result bytes (result is a list of 3 bytes)
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# First byte is ignored, we want the 2nd and 3rd bytes for our result
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value = ((result[1] & 0x03) << 8) | result[2] # Convert to 10-bit value (0-1023)
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# Extract the 12-bit ADC result from the received bytes:
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val = (ret[0] & 0x01) << 11 # Extract bit 11 (MSB)
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val |= ret[1] << 3 # Extract bits 10-3
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val |= ret[2] >> 5 # Extract bits 2-0 (shift down)
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return val & 0x0FFF # Mask to ensure only the lower 12 bits are used
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return value
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def close(self):
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"""Close SPI connection."""
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self.spi.close()
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# Example usage:
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if __name__ == "__main__":
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adc = MCP3208()
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@ -50,4 +72,3 @@ if __name__ == "__main__":
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time.sleep(0.5)
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finally:
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adc.close()
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@ -2,28 +2,32 @@
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# ======================
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# === Digital Inputs ===
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# ======================
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# Pin mappings for digital inputs (labeled on housing as 1-8)
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GPIO_DIGITAL_INPUTS = {
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1: 25, # Dig-IN_1 is connected to GPIO_25
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2: 16, # Dig-IN_2 is connected to GPIO_16
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3: 26, # Dig-IN_3 is connected to GPIO_26
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4: 13, # Dig-IN_4 is connected to GPIO_13
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5: 6, # Dig-IN_5 is connected to GPIO_6
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6: 5, # Dig-IN_6 is connected to GPIO_5
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7: 22, # Dig-IN_7 is connected to GPIO_22
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8: 24, # Dig-IN_8 is connected to GPIO_24
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0: 25, # Dig-IN_1 is connected to GPIO_25
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1: 16, # Dig-IN_2 is connected to GPIO_16
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2: 26, # Dig-IN_3 is connected to GPIO_26
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3: 13, # Dig-IN_4 is connected to GPIO_13
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4: 6, # Dig-IN_5 is connected to GPIO_6
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5: 5, # Dig-IN_6 is connected to GPIO_5
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6: 22, # Dig-IN_7 is connected to GPIO_22
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7: 24, # Dig-IN_8 is connected to GPIO_24
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}
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# ======================
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# === Shift Register ===
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# ======================
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GPIO_SHIFT_REG_DATA = 27
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GPIO_SHIFT_REG_LATCH = 17
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GPIO_SHIFT_REG_CLOCK = 4
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# FIXME: numbering in schematic is wrong (inverse) layout / terminal order matches the shift register though (left to right -> 0-7)
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# Shift Register Channel Assignments
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SHIFT_REG_CHANNEL_BUZZER = 0 # Buzzer connected to shift register channel 7
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@ -33,7 +37,9 @@ SHIFT_REG_CHANNEL_RELAY2 = 2 # Relay 2 connected to shift register channel 5
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# === ADC ===
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# ===============
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# ===== ADC =====
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# ===============
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# ADC IC is connected to RPI SPI interface 0 (pins below)
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ADC_SPI_BUS_NUM = 0
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ADC_SPI_DEVICE_NUM = 0
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@ -43,21 +49,34 @@ ADC_SPI_CS_PIN = 8 # SPI Chip Select for MCP3208
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# SCLK_0: GPIO_11
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# CE_0: GPIO# MCP3208 (ADC)
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# Pin mappings for Terminal number to actual ADC channels (due to routing they do not match)
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ADC_CHANNELS = {
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1: 0, # Channel 1 = ADC channel 0
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2: 1, # Channel 2 = ADC channel 1
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3: 2, # ...
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4: 3,
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0: 1, # Terminal 0 = ADC channel 1
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1: 0, # Terminal 1 = ADC channel 0
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2: 3, # ...
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3: 2,
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4: 5,
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5: 4,
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6: 5,
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7: 6,
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8: 7
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6: 7,
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7: 6
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}
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# Alternative to ADC_CHANNELS list have separate constants for the channels (more intuitive)
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ADC_CHANNEL_T0__0_TO_3V3 = 1
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ADC_CHANNEL_T1__0_TO_3V3 = 0
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ADC_CHANNEL_T2__0_TO_5V = 3
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ADC_CHANNEL_T3__0_TO_5V = 2
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ADC_CHANNEL_T4__0_TO_12V = 5
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ADC_CHANNEL_T5__0_TO_12V = 4
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ADC_CHANNEL_T6__0_TO_20MA = 7
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ADC_CHANNEL_T7__0_TO_20MA = 6
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# ====================
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# === SPI Terminal ===
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# ====================
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SPI_BUS_NUM = 1
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# MISO_1: GPIO_19
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# MOSI_1: GPIO_20
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@ -67,21 +86,27 @@ SPI_BUS_NUM = 1
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# ====================
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# === I2C Terminal ===
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# ====================
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GPIO_I2C_SDA = 2
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GPIO_I2C_SCL = 3
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# ===================
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# === PWM outputs ===
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# ===================
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GPIO_PWM1 = 12 # RPI_PWM0
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GPIO_PWM2 = 18 # RPI_PWM0 too
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# ====================
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# === UART / RS485 ===
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# ====================
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GPIO_UART_TX = 14 # RPI TXD
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GPIO_UART_RX = 15 # RPI RXD
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GPIO_UART_DIR = 23
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