Hi, I ran into an issue today with two new Pro Micro 3.3v 8’s where I uploaded a simple sketch, and I could not upload another sketch after that (code is below and the sketch did work fine). After mucking around all day with it, I found that re-uploading the bootloader allowed me to upload a new sketch, but only once. After further digging, I saw in Windows device manager that without a sketch loaded, the pro micro stays at the com port assigned to the bootloader (which makes sense if there’s no sketch for the bootloader to execute), allowing plenty of time to upload a new sketch. After a sketch is loaded, I just see the devices in device manager refresh several times until I end up with a com port for usb serial. So, obviously this is a problem between the pro micro and the Arduino software picking up the pro micro’s bootloader in time. I saw the note about grounding out the rst pin twice quickly giving you 8 seconds to upload a sketch, but that added about 1 second, not 8, to the bootloader com port showing in device manager. I’ve also tried about bootloaders from 4 different add on packages going back to 2012 with the same results (and no 8 second delay).
In addition, I also found a couple bugs in boards.txt on github for the 8MHz version of these. The bootloader was not set to avrdude and the efuse was set incorrectly! I’m now wondering if someone mucked up the firmware with the 8 second delay?
Any ideas on all this?
void setup() {
}
void loop() {
Serial.println("hello2");
delay(1000);
}