8 years, 3 months ago.

Possible bug in Serial attach() function with mbed 2.0 Rev 125

I think mbed 2.0 Rev 125 introduced a bug in the attach() function of the Serial class for the NUCLEO-F303K8 target. The attach() function behaves as expected for the NUCLEO-F303K8 using mbed 2.0 Rev 124 .

The same bug also seems to appear in all versions of the mbed 2.0 for the NUCLEO-L432KC target, which was first released in Rev 122.

My application uses Serial1 to read packet data from the serial output of an r/c receiver using interrupts. It uses the default Serial2 as a monitor. For safety and other reasons, the r/c transmitter is typically powered up and transmitting data prior to powering up the r/c receiver. This means that I want to be able to initialize the NUCLEO’s Serial1 and attach the interrupt with serial data present at the Rx pin of Serial1.

The function call I am using is:

rx.attach(&rx_callback,Serial::RxIrq);

My NUCLEO-F303K8 and NUCLEO-L432KC both behave as expected using mbed 2.0 Rev 125 with no data present at the Rx pin of Serial1 when the attach() function is called. The code runs and interrupts are correctly generated if I turn on the r/c transmitter to present data at the Serial1 Rx pin AFTER the interrupt has been attached.

Using mbed 2.0 Rev 125, both NUCLEO targets hang up when the attach() function is called if there is data present at the Rx pin of Serial1 when the attach() function is called.

Fortunately, NUCLEO-F303K8 works as expected using mbed 2.0 Rev 124 even if there is data present at the Rx pin of Serial1 when the attach() function is called. This makes me think that there was a change in Rev 125 that interferes with the attach() function - at least the way I am using it.

Note that I also tried RawSerial using mbed 2.0 Rev 125, but I did not see a difference in behavior.

Is there a simple workaround that will allow me to attach an interrupt to a Serial peripheral while there is data present at the Rx pin?