SPI — `pymcu.hal.spi`#

from pymcu.hal.spi import SPI

SPI bus communication in master mode. Available for AVR (ATmega328P).

class `SPI`#

`SPI(cs: str = "PB2")`#

Initializes the hardware SPI peripheral in master mode, Mode 0, MSB-first, at fosc/4 (4 MHz at 16 MHz clock). cs is the chip-select pin, auto-asserted on select().

Pinout (ATmega328P / Arduino Uno):

Pin	Arduino	Function
`PB5`	D13	SCK
`PB4`	D12	MISO
`PB3`	D11	MOSI
`PB2`	D10	SS / CS

Methods#

Method	Description
`select()`	Drive SS low (begin transaction)
`deselect()`	Drive SS high (end transaction)
`transfer(data: uint8) -> uint8`	Full-duplex byte exchange
`write(data: uint8)`	Send byte (discard received byte)
`__enter__()`	Alias for `select()` — called by `with spi:`
`__exit__()`	Alias for `deselect()` — called by `with spi:`

Examples#

Context manager (recommended)#

from pymcu.hal.spi import SPI

spi = SPI()

with spi:
    spi.write(0xAB)
    b = spi.transfer(0x00)

with spi: calls select() on enter and deselect() on exit, even if the block returns early.

74HC595 shift register#

from pymcu.hal.spi import SPI
from pymcu.time import delay_ms
from pymcu.types import uint8

def main():
    spi = SPI()
    data: uint8 = 0x01

    while True:
        with spi:
            spi.write(data)
        data = (data << 1) | (data >> 7)   # rotate left
        delay_ms(100)

SoftSPI (bit-bang)#

Use SoftSPI for arbitrary GPIO pins (no hardware SPI constraint):

from pymcu.hal.spi import SoftSPI
from pymcu.types import uint8

spi = SoftSPI(sck="PD4", mosi="PD5", miso="PD6", cs="PD7")

with spi:
    b: uint8 = spi.transfer(0x55)