How to Use MCP3425 ADC 16-Bit Mode with Raspberry Pi (Python)

Raspberry Pi cannot acquire analog values. However, Arduino is equipped with ADC as standard, but the performance is on the odder of “10-Bit(0 – 1023). The MCP3425 used in this article is 16-Bit and can also perform I2C connection. Furthermore, It’s possible to measure not only positive values but also negative values.

1  Configuration of MCP3425

The Configuration of the MCP3425 is as follows.

Diagram

Wiring diagram of MCP3425 and Raspberry Pi.

Battery Voltage Measurement Example

Check the I2C connection with the command.

$ sudo i2cdetect -y 1

2  Use MCP3425 with 16-Bit Mode

Control MCP3425 using Python. The following program acquires the analog values and display the voltage values.

$ vi mcp3425.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import smbus
import time
bus = smbus.SMBus(1)
bus.write_i2c_block_data(0x68, 0b10001000, [0x00])
time.sleep(1)

data = bus.read_i2c_block_data(0x68, 0x00, 2)
raw  = data[0] << 8 | data[1]

if raw > 32767:
   raw -= 65535
vol = 2.048 / 32767
print str(raw*vol) + " [V]"

3  Explanation

Reference : MICROCHIP – MCP3425 16-Bit Analog-to-Digital Converter with I2C Interface and On-Board Reference – Page 14

3.1  Write Setting

Refer to the above table and set the parameters. The following is the Write Setting. It’s arranged from Bit 7 to Bit 0.

bus.write_i2c_block_data(0x68, 0b10001000, [0x00])

Radix Reference

3.2  Read Setting

Receive data from MCP3425. Read using “bus.read_i2c_block_data”.

data = bus.read_i2c_block_data(0x68, 0x00, 2)

It’s necessary to properly format the read data.

raw = data[0] << 8 | data[1]

Let’s see what is contained in data[0] and data[1].

The displayed value is Decimal Number. Conversion work is done in Binary Number.

Conversion Work

Shift

About Shift :

raw = data[0] << 8 | data[1]

3.3  Measurement Result