GPIO UART(S) dropping characters

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#1,017 31 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
25/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
linux, raspberry-pi
Domain
embedded-iot

Research direction

No source files, tests, or entry points are named. Start by reviewing the linked forum post and reproducing the reported character loss at 19200 baud on full Raspbian versus Lite, including the GPU-memory setting; done means the cause is identified and characters are no longer dropped in the affected configuration.

Written by the indexing model from the issue text.

Description

Later versions of Raspbian (around 4.14.34-v7+ and beyond) seem to drop received characters from the serial uart, approx 4 characters every second or two @ 19200 baud. LITE version has NO PROBLEMS, problems show up only on full desktop versions. Dropping to 16 meg of GPU memory or below seems to solve the problem as well. More details at this post:

https://www.raspberrypi.org/forums/viewtopic.php?t=217702

Thank you!

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