Check RMT Rx level before RMT Tx?

[dmaxben]

Im using the RMT peripheral to bitbang a mult-master single-wire databus that uses CSMA/NDA to control arbitration and prevent collisions if two nodes attempt to Tx simultaneously.

I have it working for Tx/Rx, but Im having trouble with how to setup bus idle verification.

The End-Of-Frame marker for a data message is a ~300uS low level on the data line. So if the bus line has been at a low level for >300uS, the bus is considered idle and any node is free to start transmitting.

Is it possible to setup some sort of high-resolution timer on the Rx GPIO of the RMT peripheral? So when my code wants to queue a message for transmitting, the driver first looks at the Rx GPIO, and if its "low", it starts a timer...then if >300uS has elapsed and the Rx GPIO is still registering "low", it knows the bus is idle and then it can immediately begin the RMT Tx process.

Any ideas?