QUERY · ISSUE

UART sendbreak bug

openby AeroSynthopened 2022-06-21updated 2022-06-28

There is a bug with the uart.sendbreak() method with V1.17 (haven't checked the latest)

The manual states the break signal lasts 13 bits. It actually is 11.
This has caused errors with external sensors that utilize the SDI-12 protocol. .The line needs to go for at least 12ms. Now, it is 9.167 ms. Even 13 bits is not long enough.
A good solution is to add a property where you can specify how many bits you can use.
SDI-12 is popular in agriculture and other industrial applications. (www.sdi-12.org)

CANDIDATE · PULL REQUEST

esp32: Change the sendbreak duration to >= 15 bit times.

closedby robert-hhopened 2022-07-12updated 2022-08-23

port-esp32

It used to be 10 bit times, which is too short. The break state must be longer than a regular character time, at least 13 bit times. May be longer. This is implemented by changing the baud rate for sendbreak() to 2/3 of what has been configured.

Tested with a GENERIC_SPIRAM, GENERIC_C3 and UM_TINYS2 board.

Assessment

S Sonnet · high

PR #8902 directly addresses the same bug reported in issue #8794: sendbreak() generating a break signal shorter than the required minimum. The issue reports ~11 bits (9.167 ms), the PR confirms the ESP32 implementation was only 10 bit times. The fix extends it to ≥15 bit times, which satisfies SDI-12's ≥12 ms requirement. The root cause and fix are identical in substance. Classified LIKELY_DUPLICATE rather than DUPLICATE because the issue doesn't specify a port — it may affect other ports (stm32, rp2, etc.) not covered by this ESP32-only PR, and merge status is not confirmed here.

Suggested action

If PR #8902 is merged, close issue #8794 as resolved by it, but add a note that other ports may still have the same sendbreak duration bug and a follow-up issue or PR may be warranted for non-ESP32 ports.

UART sendbreak bug

esp32: Change the sendbreak duration to >= 15 bit times.

Keyboard