I'm using this crate on the MicroBit and this issue is something that started happening after I enabled the SoftDevice. UART would print half of the message and then hang there indefinitely. It's obvious what's happening in retrospect, but it sure didn't seem that way before hours of debugging.
What's happening is that the SoftDevice is triggering quite a lot of interrupts and doing its work while the main thread is paused. If it just so happens that the interrupt is triggered after the Send byte, but before the Reset TXD ready line, it's possible that the UART hardware will be done with writing the byte by the time the interrupt returns and already set the TXD ready flag, and upon return, it will be cleared and never set again. The fix is trivial - just change the order of those two operations so the TXD ready flag is cleared before the next write.
I'm kind of extrapolating that the same issue happens with the RX part though I'm not using it and didn't experience it.
I'm using this crate on the MicroBit and this issue is something that started happening after I enabled the SoftDevice. UART would print half of the message and then hang there indefinitely. It's obvious what's happening in retrospect, but it sure didn't seem that way before hours of debugging.
What's happening is that the SoftDevice is triggering quite a lot of interrupts and doing its work while the main thread is paused. If it just so happens that the interrupt is triggered after the
Send byte, but before theReset TXD readyline, it's possible that the UART hardware will be done with writing the byte by the time the interrupt returns and already set the TXD ready flag, and upon return, it will be cleared and never set again. The fix is trivial - just change the order of those two operations so the TXD ready flag is cleared before the next write.I'm kind of extrapolating that the same issue happens with the RX part though I'm not using it and didn't experience it.