from machine import Pin
from time import sleep_ms


CAN_TXD_PIN = 5
CAN_RXD_PIN = 18
BIT_TIME_MS = 80

txd = Pin(CAN_TXD_PIN, Pin.OUT, value=1)
rxd = Pin(CAN_RXD_PIN, Pin.IN, Pin.PULL_UP)


def write_can_bit(bit):
    # SN65HVD230 logic: TXD LOW = dominant, TXD HIGH = recessive.
    txd.value(1 if bit else 0)
    sleep_ms(BIT_TIME_MS)
    print("TXD:", txd.value(), "RXD:", rxd.value())


def send_demo_frame():
    bits = [
        0,  # SOF, dominant
        1, 0, 1, 0, 0, 1, 1, 0,
        1, 1, 1, 1, 1,
    ]

    for bit in bits:
        write_can_bit(bit)

    txd.value(1)
    sleep_ms(300)


print("ESP32 MicroPython SN65HVD230 demo")
print("GPIO5 -> TXD, GPIO18 <- RXD")

while True:
    send_demo_frame()