QUERY · ISSUE

Data loss in string transfer through sys.stdout.write

openby pchalaopened 2023-07-18updated 2024-10-06

bugport-rp2

Env: MicroPython v1.20.0 on 2023-04-26; Raspberry Pi Pico with RP2040

I have noticed constant data loss when transfer string objects with help of sys.stdout.write() method.

MCU code:

import sys

BUF_SIZE = 10000

while True:
    sys.stdin.readline()
    line = bytes(BUF_SIZE).hex() + '\n'
    sys.stdout.write(line)

PC code:

import serial
connection = serial.Serial('COM6', timeout=3)
for i in range(1000):
    connection.write(b'\n')
    res = connection.readline()
    print(i, len(res))

If BUF_SIZE set to 8000 everything will work fine.

In case of sending bytes:

import sys

BUF_SIZE = 40000

while True:
    sys.stdin.readline()
    line = bytes(BUF_SIZE)
    sys.stdout.write(line)

transfer is ok even for 40000 bytes.

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

Q Qwen · medium

Both issues are RP2040 port bugs involving sys.stdin/stdout operations and buffer handling. However, they address different specific problems: Issue #12037 reports data loss in sys.stdout.write() when transferring large hex-encoded strings (>8KB), while Issue #11253 reports failures in sys.stdin.read(64) and sys.stdin.readline() when the input buffer contains multiples of 64 bytes. The symptoms, affected operations (write vs read), and specific failure conditions are different. While they may share a common root cause in the RP2 UART driver or buffer management, they are distinct bugs that would require separate fixes.

Suggested action

Keep both issues open as they describe different problems. The maintainer may want to review if they share a common underlying cause in the RP2 UART driver that could be addressed with a single fix.

Data loss in string transfer through sys.stdout.write

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

Keyboard