QUERY · ISSUE

read() & readline() on rp2 port don't work/work as expected

openby uksconeopened 2021-02-05updated 2021-02-13

port-rp2

the UART on the rp2 port mostly works. read([num of bytes]) works mostly as expected although it seems to drop bytes occasionally and "hangs" if you try to read more bytes than currently available however read() with no number of bytes to read set and readline() just sit there indefinitely. I suspect it's to do with the fact that timeout isn't implemented

CANDIDATE · ISSUE

On RP2 sys.stdin.read(64) and sys.stdin.readline() do not work if we have multiple of 64 bytes in buffer

closedby pchalaopened 2023-04-13updated 2023-04-25

port-rp2

MicroPython v1.19.1-994-ga4672149b on 2023-03-29; Raspberry Pi Pico with RP2040

Pico code:

import sys

while True:
    line = sys.stdin.read(64)
    print(len(line))

Assessment

S Sonnet · high

Both issues involve read()/readline() failures on the rp2 port, but they are distinct bugs. Issue #6851 concerns machine.UART where read() and readline() hang indefinitely due to missing timeout implementation. Issue #11253 concerns sys.stdin where read(64) and readline() fail specifically when the input buffer contains multiples of the requested read size — a buffer chunking/management bug, not a timeout issue. Different interfaces (machine.UART vs sys.stdin), different root causes (missing timeout vs incorrect handling of multi-chunk buffers), and different failure conditions (unconditional hang vs conditional failure based on buffer fill level).

Suggested action

No closure action needed. Link the issues as related context for anyone investigating rp2 read/readline behaviour. They may share underlying stream infrastructure but require separate fixes.

read() & readline() on rp2 port don't work/work as expected

On RP2 sys.stdin.read(64) and sys.stdin.readline() do not work if we have multiple of 64 bytes in buffer

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