fix(SoftwareSerial): correct TX to RX switch when using half-duplex #1771
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ABOSTM
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Jul 26, 2022
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@dominikberse
thanks for sharing your findings.
Patch LGTM
julien33510
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Oct 2, 2023
mise en place de la librairie semi-duplex trouvé sur github (stm32duino/Arduino_Core_STM32#1771) et ajout de la spécificité pour les bits de parité et les 2 bits stop => succès
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Summary
When working with single-pin half-duplex SoftwareSerial, I noticed that after the call to
listen()receiving data is not possible until data is written. In factsetRXTX(true)is only called withinsend(), which in turn is only called as long asactive_outis set (i.e. ongoing transmission). Since at the beginning oflisten()completion of any ongoing transmissions is awaited, the SoftwareSerial will not actively listen before another transmission is completed.This PR fixes/implements the following bugs/features
This occurs if the communication is not initiated by the STM32. Otherwise, one would simply call
listen()and then send whatever will trigger the other side to respond.In my case, I wanted to use a second line to indicate the direction of communication (which however can not be used as a second line for full-duplex). I must admit that this is probably a very rare case, and the fix I suggest will in fact change the current behavior of calling
listen()before sending data. However it took me a few hours to debug this and I thought I should at least mention this finding in case someone else stumbles upon it.