Restore ability to read usb_cdc buffer when serial client is disconnected #10177
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…l client is connected the original issue is fixed in tinyusb
dhalbert
approved these changes
Mar 24, 2025
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Tested on a Metro M4, using the test program in #7456. Then I tried the build from here, and confirmed that it reads characters normally through tio. Then i did echo abc >/dev/ttyACM1 and confirmed the problem in 9.2.6 and the fix (behaved as desired) in the PR artifact.
Thank you for keeping this on your plate!
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This is a fix for the issue I mentioned all the way here: #7456 (comment)
The issue mentioned in #6018 is now fixed in tinyusb: hathach/tinyusb#2630
The original solution in #7100 caused the buffer to contain inaccessible data, requiring a serial software on the host to be connected to be able to read the buffer (asserting DTR). Another solution would be to test
tud_ready()ortud_cdc_n_ready()instead of connected, but that would be redundant with the tinyusb fix.I was not able to reproduce #6018 with that PR.