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matthiasbock / oled-control-board

A little PCB with an STM32F4 MCU to control an Adafruit 1.5" OLED display board. Designed with KiCad 5.
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v1.0: Debugging problems #2

Open matthiasbock opened 5 years ago

matthiasbock commented 5 years ago

OpenOCD won't connect. Is it due to the missing quartz? Is a quartz required for SWD to work? I though, the internal RC would be sufficient...

3V3 are present at the MCU. Capacitors and resistors are equipped. Both SWD signals arrive on the MCU pins.

matthiasbock commented 5 years ago

The official datasheet states:

On reset the 16 MHz internal RC oscillator is selected as the default CPU clock...
This clock can be monitored for failure. If a failure is detected, the system
automatically switches back to the internal RC oscillator...
matthiasbock commented 5 years ago

I desoldered the microcontroller, soldered a new one and, considering issue #3, added a patch cable to supply pin 13 (VDDA) with 3.3V. After that OpenOCD could successfully establish a connection to the MCU. After removing the patch cable, it ceased to work again i.e. the debugger could not establish a connection to the MCU anymore. Re-attaching the patch cable and it worked again.

Conclusion: VDDA must not be left open, but must be connected to a supply voltage, otherwise the MCU won't be debuggable (probably won't run at all).