# I2C INSTRUCTIONS

> Source: https://maker.tdlogy.com/wiki-doc/quecpython-eg800k-eg800ak-i2c-instructions/

EG800K & EG800AK Module — Part 2: I2C

This document instructs I2C communication on QuecPython (module machine. I2C), including initialization, register read/write, address scanning on the bus, and a real-world example of reading the accelerometer SC7A20HTR via I2C2 on the EG800K.

# 1. Overview

I2C (Inter-Integrated Circuit) is a 2-wire serial communication standard (SCL – clock, SDA – data), commonly used to connect sensors, EEPROM, RTC, etc. with modules. On QuecPython, I2C is manipulated through the machine layer. I2C, works in master mode.

Important Note: The number of I2Cn channels (I2C0/I2C1/I2C2) and the corresponding pair of SCL/SDA pins are fixed according to the hardware of each module line — not reconfigurable with code. Check the Hardware Design/pinout of the EG800K or EG800AK to see which I2C channel is being given which pin on the board you are using.

# 2. Layer Machine. I2C

## 2.1. Initialization

from machine import I2C# I2C(I2Cn, mode)i2c = I2C(I2C. I2C2, I2C. STANDARD_MODE)

ParameterTypeMeaningI2CnintPhysical I2C channel: I2C. I2C0, I2C. I2C1, I2C. I2C2... (depending on how many channels the model supports).modeintBus speed: STANDARD_MODE (100kHz), FAST_MODE (400kHz), some models have ENHANCED_FAST_MODE.

Each I2C channel should only initialize (create an object) once in the entire program. If you have multiple devices sharing a bus, simply create an I2C object and share a different slave address when calling read()/write().

## 2.2. Write() Method — Register Recording

i2c.write(slave_addr, reg_addr, addr_len, data, data_len)

ParameterMeaningslave_addrThe 7-bit I2C address of the slave device.reg_addrbytearray contains the register address to be written to (e.g. bytearray([0x20]))).addr_lenThe number of bytes of reg_addr (usually 1).dataThe bytearray contains the data to be written.data_lenThe number of bytes of data to be written.

## 2.3. Read() method — reads registers

i2c.read(slave_addr, reg_addr, addr_len, r_data, data_len, delay)

ParameterMeaningslave_addrThe 7-bit I2C address of the slave device.reg_addrThe bytearray contains the register address to be read.addr_lenThe number of bytes of reg_addr.r_dataempty bytearray to receive the read data about (size = data_len).data_lenThe number of bytes to read.DelayTime-out (ms) between sending an address and reading data—some sensors need processing time before returning results.

Note about data types: The register address (reg_addr) and data (data/r_data) parameters are required to be bytearray, not int or regular list passes — this is a very common mistake when switching from MicroPython/Arduino to QuecPython. Both read()/write() functions return the result code (0 = success), so check the return value to debug when the communication fails.

# 3. Address scan on the bus (I2C scan)

Before writing a driver for a new sensor, it is recommended to scan the entire I2C address range (0x03–0x77) to confirm if the device is responsive (ACK), and what the actual address is—many sensors have 2 addresses available depending on the SDO/SA0 pin logic level (GND or VDD connection).

# 4. Practical example: reading SC7A20HTR accelerometer (EG800K, I2C2)

The demo below illustrates the entire process above: scan the bus to determine the address, initialize the sensor via the configuration register, read the recognition register (WHO_AM_I) to confirm the communication, and then read the 3-axis acceleration data continuously.

## 4.1. Driver process

## 4.2. Test run results

The REPL snapshot below (QPYcom) shows a bus scan that finds the device at the 0x19 address, reads WHO_AM_I=0x11 to confirm the sensor is correct, and then continuously prints the real-time 3-axis acceleration value—Z data ≈ 1g when the sensor is at rest (gravity), and change in direction when tilting/shaking the board.

Full Source Code (GitHub): https://github.com/quanminhwork2404-create/DEMO-EG800K-EG800AK/blob/main/project/EG800K_SC7A20_I2C.py

# 5. Practical differences between EG800K and EG800AK

# 6. Common mistakes

PhenomenonCommon causesHow to handleI2C.write()/read() returns another 0Wrong slave address, missing pull-up, or wrong SCL/SDA pinRun i2c_scan() to confirm the address and if the bus is responsiveTypeError when calling write()/read()Pass int or list instead of bytearray for address/data parametersAlways wrap the value with bytearray([...]) before transmittingWHO_AM_I other readable datasheetWrong register address, not enabled auto-increment when reading multiple bytes, or misreading the sensorReconcile the datasheet, check the MSB bit of the register address when reading consecutivelyContinuous false/noise reading dataLack of delay between command and read, or sensor instability after configurationAdd sleep_ms() after the configuration register recording steps, using the delay parameter of read() if the sensor requires it

# 7. References

The next part (SPI, UART, DVP Camera, etc.) will be added in the next documents.