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uart_rx: Fix incorrect handshaking 

AXI stream is transferred exactly on the rising edge of the clock. Use
the current value of the signals for this, instead of past values.
Simulate a slower slave to ensure this is tested.

Fixes: a549fca ("Add UART receive module")
Signed-off-by: Sean Anderson <seanga2@gmail.com>
This commit is contained in:
Sean Anderson 2023-03-04 16:41:56 -05:00
parent 10a4199381
commit 067029ad3b
2 changed files with 13 additions and 5 deletions
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4
rtl/uart_rx.v
View File

@ -1,6 +1,6 @@
// SPDX-License-Identifier: AGPL-3.0-Only
/*
* Copyright (C) 2022 Sean Anderson <seanga2@gmail.com>
* Copyright (C) 2023 Sean Anderson <seanga2@gmail.com>
*
* 8n1@115200; no one uses anything else (and neither do I)
*/
@ -56,7 +56,7 @@ module uart_rx (
lfsr_next = { lfsr[9:0], lfsr[10] ^ lfsr[8] };
bits_next = bits;
data_next = data;
valid_next = valid && !ready_last;
valid_next = valid && !ready;
overflow_next = 0;
frame_error_next = 0;

14
tb/uart_rx.py
View File

@ -4,10 +4,12 @@
import cocotb
from cocotb.binary import BinaryValue
from cocotb.clock import Clock
from cocotb.regression import TestFactory
from cocotb.triggers import FallingEdge, Timer
from cocotb.utils import get_sim_time, get_sim_steps
from .axis_replay_buffer import recv_packet
from .util import ClockEnable, timeout
BAUD = 4e6
BIT_STEPS = get_sim_steps(1 / BAUD, 'sec', round_mode='round')
@ -22,11 +24,11 @@ async def putchar(rx, c):
rx.value = bit
await Timer(BIT_STEPS)
@cocotb.test(timeout_time=1, timeout_unit='ms')
async def test_rx(uart):
@timeout(1, 'ms')
async def test_rx(uart, ratio):
uart.clk.value = BinaryValue('Z')
uart.rst.value = 1
uart.ready.value = 1
uart.ready.value = 0
uart.rx.value = 1
uart.high_speed.value = 1
@ -34,6 +36,7 @@ async def test_rx(uart):
uart.rst.value = 0
await cocotb.start(Clock(uart.clk, 8, units='ns').start())
await FallingEdge(uart.clk)
ce = await cocotb.start(ClockEnable(uart.clk, uart.ready, ratio))
msg = b"Hell\0"
signals = {
@ -68,6 +71,7 @@ async def test_rx(uart):
assert frame_errors == 1
ce.kill()
uart.ready.value = 0
await putchar(uart.rx, 0xFF)
await putchar(uart.rx, 0)
@ -78,3 +82,7 @@ async def test_rx(uart):
await recv_packet(signals, (0xFF,))
monitor.kill()
uart_tests = TestFactory(test_rx)
uart_tests.add_option('ratio', (1, 4))
uart_tests.generate_tests()