Fix ADC-lib to use 12Bit, Rework read_analog example + channel mapping

rpi-scripts/examples/read_analog_inputs.py

@@ -7,14 +7,70 @@ import time
 # Include custom files
 # Add the parent directory to the module search path
 sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), "..")))
-from interface_board_libs.adc_mcp3208 import MCP3208
+from interface_board_libs.adc_mcp3208 import MCP3208 # custom driver for ADC-IC
-from interface_board_pins import ADC_CHANNELS
+from interface_board_pins import ( 
+    ADC_CHANNELS,
+
+    ADC_CHANNEL_T0__0_TO_3V3,
+    ADC_CHANNEL_T1__0_TO_3V3,
+    ADC_CHANNEL_T2__0_TO_5V,
+    ADC_CHANNEL_T3__0_TO_5V,
+    ADC_CHANNEL_T4__0_TO_12V,
+    ADC_CHANNEL_T5__0_TO_12V,
+    ADC_CHANNEL_T6__0_TO_20MA,
+    ADC_CHANNEL_T7__0_TO_20MA,
+) # mapping of ADC channels to terminals
 
 
+# create ADC instance 
 adc = MCP3208()
 
+
+
+# local helper function to scale the adc value to an actual voltage
+def adc2value(adc_value, max_value):
+    max_adc = 4095
+    return adc_value * max_value / max_adc
+
+
+
+
 while True:
-        print ("==================")
+        print ("")
-        for i in range(8):
+
-                print('ADC[{}]: {:.2f}'.format(i, adc.read(i)))
+        # Read all available channels in a loop according to terminal order / map
-        time.sleep(0.5)
+        values = []
+        for terminal, adc_channel in ADC_CHANNELS.items():
+            value = adc.read(adc_channel)
+            print(f"T{terminal}: ADC={value:04d}  => U_ADC = {adc2value(value, 3.3):5.3f}V")
+        
+
+        # Read channels one by one using defined constants (more intuitive)
+        print("-" * 40)  
+        value = adc.read(ADC_CHANNEL_T0__0_TO_3V3)  
+        print(f"Terminal 0 (0 to 3.3V): ADC={value:04d} => Terminal={adc2value(value, 3.3):4.2f}V")  
+
+        value = adc.read(ADC_CHANNEL_T1__0_TO_3V3)  
+        print(f"Terminal 1 (0 to 3.3V): ADC={value:04d} => Terminal={adc2value(value, 3.3):4.2f}V")  
+
+        value = adc.read(ADC_CHANNEL_T2__0_TO_5V)  
+        print(f"Terminal 2 (0 to 5V):   ADC={value:04d} => Terminal={adc2value(value, 5):4.2f}V")  
+
+        value = adc.read(ADC_CHANNEL_T3__0_TO_5V)  
+        print(f"Terminal 3 (0 to 5V):   ADC={value:04d} => Terminal={adc2value(value, 5):4.2f}V")  
+
+        value = adc.read(ADC_CHANNEL_T4__0_TO_12V)  
+        print(f"Terminal 4 (0 to 12V):  ADC={value:04d} => Terminal={adc2value(value, 12):05.2f}V")  
+
+        value = adc.read(ADC_CHANNEL_T5__0_TO_12V)  
+        print(f"Terminal 5 (0 to 12V):  ADC={value:04d} => Terminal={adc2value(value, 12):05.2f}V")  
+
+        value = adc.read(ADC_CHANNEL_T6__0_TO_20MA)  
+        print(f"Terminal 6 (0 to 20mA): ADC={value:04d} => Terminal={adc2value(value, 20):05.2f}mA")  
+
+        value = adc.read(ADC_CHANNEL_T7__0_TO_20MA)  
+        print(f"Terminal 7 (0 to 20mA): ADC={value:04d} => Terminal={adc2value(value, 20):05.2f}mA")  
+
+        print("-" * 40)  
+        time.sleep(1)  # Delay before next read cycle  
+

rpi-scripts/interface_board_libs/adc_mcp3208.py

@@ -1,6 +1,9 @@
 import spidev
 import time
 
+DEBUG = False
+
+
 class MCP3208:
     def __init__(self, bus=0, device=0):
         # Initialize SPI bus and device
@@ -9,36 +12,55 @@ class MCP3208:
         self.spi.max_speed_hz = 1000000  # Adjust based on your needs (e.g., 1MHz)
         self.spi.mode = 0b00  # Set SPI mode (Mode 0 for MCP3208)
     
+
     def read(self, channel):
         """
         Read the ADC value from the specified channel (0-7).
         """
+
+        # MCP3208 is a 12-bit SPI ADC. Communication requires sending a 3-byte command and receiving a 3-byte response.
+        # The bits in the command sequence are structured as follows:
+    
+        # Command Byte (8 bits):  
+        # | Start (1) | Mode (1) | Channel (3) | Padding (3) |
+    
+        # The MCP3208 responds with 3 bytes:
+        # - Byte 1: Contains the highest bit (bit 11) of the 12-bit ADC result.
+        # - Byte 2: Contains bits 10-3 of the ADC result.
+        # - Byte 3: Contains bits 2-0 of the ADC result.
+
+        # Ensure the channel is valid (0-7)
         if channel < 0 or channel > 7:
-            raise ValueError("Channel must be between 0 and 7.")
+            raise ValueError(f"Channel must be between 0 and 7. (current channel={channel})")
 
-        # MCP3208 sends a 3-byte response, which needs to be processed
+        # Construct the command byte sequence:
-        # Start with the single bit control byte, followed by the channel selection
+        # - Start bit (1)  -> 1000 0000 (0x80)
-        # MCP3208 uses 3 bits for the channel: 0-7
+        # - Single-ended (1) -> 1100 0000 (0xC0)
-        # The command byte looks like this:
+        # - Channel (3 bits) shifted into position
-        # |  Start | Single-ended | Channel (3 bits) | Don't Care (1 bit) |
+        cmd = 0x80  # Start bit: 1000 0000
+        cmd |= 0x40  # Single-ended mode: 1100 0000
+        cmd |= (channel & 0x07) << 3  # Move channel number to bits 5-3
 
-        # Construct the 3-byte command
+        # Send the command and receive the 3-byte response
-        # Start bit (1) | Single-ended (1) | Channel (3 bits) | Don't care (1) | End (1)
+        ret = self.spi.xfer2([cmd, 0x00, 0x00])  # Send 3 bytes, receive 3 bytes
-        command = [1, (8 + channel) << 4, 0]
 
-        # Send command and receive the 3-byte result
+        if DEBUG:
-        result = self.spi.xfer2(command)
+            print(f"result[0]: {bin(ret[0])}, result[1]: {bin(ret[1])}, result[2]: {bin(ret[2])}")
 
-        # Combine the result bytes (result is a list of 3 bytes)
+        # Extract the 12-bit ADC result from the received bytes:
-        # First byte is ignored, we want the 2nd and 3rd bytes for our result
+        val = (ret[0] & 0x01) << 11  # Extract bit 11 (MSB)
-        value = ((result[1] & 0x03) << 8) | result[2]  # Convert to 10-bit value (0-1023)
+        val |= ret[1] << 3  # Extract bits 10-3
+        val |= ret[2] >> 5  # Extract bits 2-0 (shift down)
+
+        return val & 0x0FFF  # Mask to ensure only the lower 12 bits are used
     
-        return value
 
     def close(self):
         """Close SPI connection."""
         self.spi.close()
 
+
+
 # Example usage:
 if __name__ == "__main__":
     adc = MCP3208()
@@ -50,4 +72,3 @@ if __name__ == "__main__":
             time.sleep(0.5)
     finally:
         adc.close()
-

rpi-scripts/interface_board_pins.py

@@ -2,28 +2,32 @@
 
 
 
+
+# ======================
 # === Digital Inputs ===
+# ======================
 # Pin mappings for digital inputs (labeled on housing as 1-8)
 GPIO_DIGITAL_INPUTS = {
-    1: 25,  # Dig-IN_1 is connected to GPIO_25
+    0: 25,  # Dig-IN_1 is connected to GPIO_25
-    2: 16,  # Dig-IN_2 is connected to GPIO_16
+    1: 16,  # Dig-IN_2 is connected to GPIO_16
-    3: 26,  # Dig-IN_3 is connected to GPIO_26
+    2: 26,  # Dig-IN_3 is connected to GPIO_26
-    4: 13,  # Dig-IN_4 is connected to GPIO_13
+    3: 13,  # Dig-IN_4 is connected to GPIO_13
-    5: 6,   # Dig-IN_5 is connected to GPIO_6
+    4: 6,   # Dig-IN_5 is connected to GPIO_6
-    6: 5,   # Dig-IN_6 is connected to GPIO_5
+    5: 5,   # Dig-IN_6 is connected to GPIO_5
-    7: 22,  # Dig-IN_7 is connected to GPIO_22
+    6: 22,  # Dig-IN_7 is connected to GPIO_22
-    8: 24,  # Dig-IN_8 is connected to GPIO_24
+    7: 24,  # Dig-IN_8 is connected to GPIO_24
 }
 
 
 
 
+# ======================
 # === Shift Register ===
+# ======================
 GPIO_SHIFT_REG_DATA = 27
 GPIO_SHIFT_REG_LATCH = 17
 GPIO_SHIFT_REG_CLOCK = 4
 
-
 # FIXME: numbering in schematic is wrong (inverse) layout / terminal order matches the shift register though (left to right -> 0-7)
 # Shift Register Channel Assignments
 SHIFT_REG_CHANNEL_BUZZER = 0  # Buzzer connected to shift register channel 7
@@ -33,7 +37,9 @@ SHIFT_REG_CHANNEL_RELAY2 = 2  # Relay 2 connected to shift register channel 5
 
 
 
-# === ADC ===
+# ===============
+# ===== ADC =====
+# ===============
 # ADC IC is connected to RPI SPI interface 0 (pins below)
 ADC_SPI_BUS_NUM = 0  
 ADC_SPI_DEVICE_NUM = 0
@@ -43,21 +49,34 @@ ADC_SPI_CS_PIN = 8  # SPI Chip Select for MCP3208
 # SCLK_0: GPIO_11
 # CE_0:   GPIO# MCP3208 (ADC)
 
+# Pin mappings for Terminal number to actual ADC channels (due to routing they do not match)
 ADC_CHANNELS = {
-    1: 0,  # Channel 1 = ADC channel 0
+    0: 1,  # Terminal 0 = ADC channel 1
-    2: 1,  # Channel 2 = ADC channel 1
+    1: 0,  # Terminal 1 = ADC channel 0
-    3: 2,  # ...
+    2: 3,  # ...
-    4: 3,
+    3: 2,
+    4: 5,
     5: 4,
-    6: 5,
+    6: 7,
-    7: 6,
+    7: 6
-    8: 7
 }
 
+# Alternative to ADC_CHANNELS list have separate constants for the channels (more intuitive)
+ADC_CHANNEL_T0__0_TO_3V3  = 1
+ADC_CHANNEL_T1__0_TO_3V3  = 0
+ADC_CHANNEL_T2__0_TO_5V   = 3
+ADC_CHANNEL_T3__0_TO_5V   = 2
+ADC_CHANNEL_T4__0_TO_12V  = 5
+ADC_CHANNEL_T5__0_TO_12V  = 4
+ADC_CHANNEL_T6__0_TO_20MA = 7
+ADC_CHANNEL_T7__0_TO_20MA = 6
 
 
 
+
+# ====================
 # === SPI Terminal ===
+# ====================
 SPI_BUS_NUM = 1
 # MISO_1: GPIO_19
 # MOSI_1: GPIO_20
@@ -67,21 +86,27 @@ SPI_BUS_NUM = 1
 
 
 
+# ====================
 # === I2C Terminal ===
+# ====================
 GPIO_I2C_SDA = 2
 GPIO_I2C_SCL = 3
 
 
 
 
+# ===================
 # === PWM outputs ===
+# ===================
 GPIO_PWM1 = 12  # RPI_PWM0
 GPIO_PWM2 = 18  # RPI_PWM0 too
 
 
 
 
+# ====================
 # === UART / RS485 ===
+# ====================
 GPIO_UART_TX = 14 # RPI TXD
 GPIO_UART_RX = 15 # RPI RXD
 GPIO_UART_DIR = 23