I2C — `pymcu.hal.i2c`#

from pymcu.hal.i2c import I2C

I2C (TWI) bus communication. Available for AVR (ATmega328P).

Pinout (ATmega328P / Arduino Uno):

Signal	Pin	Arduino
SDA	`PC4`	A4
SCL	`PC5`	A5

class `I2C`#

`I2C(freq: uint32 = 100000)`#

Initializes the TWI peripheral. Default frequency is 100 kHz.

Status constants#

Constant	Value	Meaning
`I2C.START`	`0x08`	START condition transmitted
`I2C.SLA_ACK`	`0x18`	SLA+W transmitted, ACK received
`I2C.SLA_NACK`	`0x20`	SLA+W transmitted, NACK received
`I2C.DATA_ACK`	`0x28`	Data byte transmitted, ACK received
`I2C.SLA_R_ACK`	`0x40`	SLA+R transmitted, ACK received

Methods#

Method	Description
`ping(addr: uint8) -> uint8`	Returns 1 if device ACKs, 0 if NACK
`start() -> uint8`	Send START condition, return status
`stop()`	Send STOP condition
`write(data: uint8) -> uint8`	Write byte, return TWI status
`write_to(addr: uint8, data: uint8) -> uint8`	START + SLA+W + byte + STOP
`write_bytes(addr: uint8, buf, n: uint8)`	Multi-byte write: START + SLA+W + N bytes + STOP
`read_from(addr: uint8) -> uint8`	START + SLA+R + read byte + NACK + STOP
`read_ack() -> uint8`	Read byte + send ACK (more data follows)
`read_nack() -> uint8`	Read byte + send NACK (last byte in transaction)
`__enter__() -> uint8`	Alias for `start()` — called by `with i2c:`
`__exit__()`	Alias for `stop()` — called by `with i2c:`

Examples#

Bus scanner#

from pymcu.hal.i2c import I2C
from pymcu.hal.uart import UART
from pymcu.types import uint8

def main():
    i2c = I2C()
    uart = UART(9600)
    uart.println("Scanning I2C bus...")

    addr: uint8 = 1
    while addr < 128:
        if i2c.ping(addr):
            uart.write_str("Found: 0x")
            uart.print_byte(addr)
        addr += 1

Read a register (context manager)#

from pymcu.hal.i2c import I2C
from pymcu.types import uint8

def read_reg(i2c: I2C, dev_addr: uint8, reg: uint8) -> uint8:
    # Write register address
    with i2c:
        i2c.write((dev_addr << 1) | 0)   # SLA+W
        i2c.write(reg)

    # Read one byte
    result: uint8 = 0
    with i2c:
        i2c.write((dev_addr << 1) | 1)   # SLA+R
        result = i2c.read_nack()
    return result

SoftI2C (bit-bang)#

Use SoftI2C for arbitrary GPIO pins:

from pymcu.hal.i2c import SoftI2C
from pymcu.types import uint8

i2c = SoftI2C(sda="PD2", scl="PD3")
found: uint8 = i2c.ping(0x68)      # check MPU-6050