UART Drivers

Native UART Source (transmitter) and Sink (receiver) BFMs for cocotb testbenches. Pure-Python implementation with configurable baud rate, data width (5–9 bits), parity, and stop bits. Includes error injection methods for testing UART receiver robustness.

Quick Start

import cocotb
from routertl.sim import Tb, UartSource
from routertl.sim.cocotb.tb.drivers.uart_master import UartSink

@cocotb.test()
async def test_uart_loopback(dut):
    tb = Tb(dut)
    await tb.start_clock()
    await tb.reset()

    # Transmit data into the DUT's RX pin
    uart_tx = UartSource(dut.UART_RX, baud=115200, bits=8, parity="none")
    await uart_tx.write_bytes([0xDE, 0xAD, 0xBE, 0xEF])

    # Capture data coming out of the DUT's TX pin
    uart_rx = UartSink(dut.UART_TX, baud=115200, bits=8, parity="none")
    cocotb.start_soon(uart_rx.start())

    # Wait and read
    for _ in range(4):
        byte = await uart_rx.read(timeout_us=1000)
        tb.log.info(f"Received: 0x{byte:02X}")

Error Injection

The UartSource includes methods for testing receiver error handling:

# Send a byte with a bad stop bit (framing error)
await uart_tx.inject_framing_error(0xAA)

# Send a byte with inverted parity (parity error)
await uart_tx.inject_parity_error(0x55)

# Send a UART break condition (line held low)
await uart_tx.send_break(duration_bits=12)

Configuration

Classes

::: sim.cocotb.tb.drivers.uart_master.UartConfig options: show_root_heading: true

::: sim.cocotb.tb.drivers.uart_master.UartSource options: show_root_heading: true show_source: true members: - init - write - write_bytes - send_break - inject_framing_error - inject_parity_error

::: sim.cocotb.tb.drivers.uart_master.UartSink options: show_root_heading: true show_source: true members: - init - start - read - read_nowait - empty - count