When transmitting, waiting a while after tx_enable is necessary before calling the transmit function.
The interrupt happens if you call it too early but the openmote doesn’t hear anything.
From p. 77 of Sahar’s thesis (https://www2.eecs.berkeley.edu/Pubs/TechRpts/2016/EECS-2016-71.pdf) it looks like the necessary delay might be from the TX FIFO being loaded.
Need to figure out a way to determine when the FIFO is finished loading so the waiting isn’t open loop. Current code is 8 ms but @Tengfei Chang experimented and 0.5 ms wait time works.