Closed
Description
I discovered a fault in USB driver in SAMD 1.6.7, where a call to SerialUSB.available() always will return true, after a single character has been sent to the USB endpoint.
following test sketch will show the error:
void setup() {
// put your setup code here, to run once:
SerialUSB.begin(115200);
while (!Serial) {}
SerialUSB.println("Test sketch");
}
void loop() {
// put your main code here, to run repeatedly:
SerialUSB.print("test ");
SerialUSB.println(millis());
delay(1000);
if (SerialUSB.available()) {
SerialUSB.print(" Received ");
SerialUSB.println(SerialUSB.read());
}
}
The output with SAMD 1.6.7 package is:
Test sketch
test 1120
test 2120
test 3120
test 4120
test 5120
test 6120
Received 32
test 7120
Received -1
test 8120
Received -1
test 9120
Received -1
test 10120
Received -1
test 11120
Received -1
test 12120
Received -1
test 13120
while with SAMD 1.6.6 package installed:
Test sketch
test 810
test 1810
test 2810
test 3810
test 4810
test 5810
Received 32
test 6810
test 7810
test 8810
Received 32
test 9810
test 10810
test 11810
The error wil result in an endless loop, if you have a while(SerialUSB.available()) {} to read characters from the serial device.