PublicStatic
New member
I have the preprogrammed PJRC MKL02Z32 bootloader connected to the blank MKL26Z64VFT4 by way of a USB-C connection and I am having some trouble getting things working. The USB-C connection was meant to allow the bootloader and MCU to exist on two separate boards so that the MCU board could be made smaller, and the bootloader would only be attached when programming was required. I have another design that has the bootloader on the same board as the MCU and that works just fine. When I move things to the new two-board configuration I get strange behaviors from the bootloader.
I'm seeing the expected pulse train at 30 kHz on the RESET pin of the MCU and the 3.3V line, along with everything else, looks good on the MCU board. When I press the PROGRAM button on the bootloader board the RESET pin on the MCU is indeed pulled LOW, so that is working. This is when the curious behavior starts however. The SWD-IO pin shows a constant 2V signal and SWD-CLK line is constant LOW. I believe I have verified that the pins are indeed making good contact with no shorts, bridges, or opens. When I set a trigger for the single shot, I can see something trying to happen at the very start, but that seems to fail and it goes to the steady 2V/GND state.
I have seen other behaviors from the bootloader where the IO line will continuously send a pulse packet and the clock line will do the same. The IO and CLK signals appeared to be aligned correctly, but MCU seems to be resetting out of sync. It's like the bootloader is trying to program the MCU but the MCU is not listening.
Any suggestions on how to trouble shoot this issue or what could be wrong with the circuit would be greatly appreciated. I'm at my wits end on this one...
RESET Pin:
Constant CLK and IO pins:
Single-shot start of programming:
USB configuration:
MCU pins:
Bootloader pins:
Bootloader trying to program the MCU:
CLK and RESET out of sync:
I'm seeing the expected pulse train at 30 kHz on the RESET pin of the MCU and the 3.3V line, along with everything else, looks good on the MCU board. When I press the PROGRAM button on the bootloader board the RESET pin on the MCU is indeed pulled LOW, so that is working. This is when the curious behavior starts however. The SWD-IO pin shows a constant 2V signal and SWD-CLK line is constant LOW. I believe I have verified that the pins are indeed making good contact with no shorts, bridges, or opens. When I set a trigger for the single shot, I can see something trying to happen at the very start, but that seems to fail and it goes to the steady 2V/GND state.
I have seen other behaviors from the bootloader where the IO line will continuously send a pulse packet and the clock line will do the same. The IO and CLK signals appeared to be aligned correctly, but MCU seems to be resetting out of sync. It's like the bootloader is trying to program the MCU but the MCU is not listening.
Any suggestions on how to trouble shoot this issue or what could be wrong with the circuit would be greatly appreciated. I'm at my wits end on this one...
RESET Pin:
Constant CLK and IO pins:
Single-shot start of programming:
USB configuration:
MCU pins:
Bootloader pins:
Bootloader trying to program the MCU:
CLK and RESET out of sync: