It is very difficult to debug it. New issues occur, old ones disappear at random time...
I checked all pins of the MCU under microscope. I didn't found any problem. I re-soldered all pins one-by-one manually. After this, the MCU was able to run with crystal at 250 MHz.Unless I closed the back cover. After closing the cover, it was not able to start the crystal more. I changed clock to internal RC, 250 MHz. It runs...
The most recent issues:
- Spikes at 62 and 125 MHz rate, noise only; open or short input, baseline in middle. I think not all bits from the ADC are read in the time. The result is a mixture of bits from 0x7f and 0x80. Rate of the spikes depends on the CPU activity. Pressing the 1/10X button increases the rate little, trigger level button more. After shifting the baseline level, the spikes disappear. The spikes are not present always. Sometime immediately after power on, sometime after some time...
- "Flash error"; reading signature bytes failed. I saw this error today two times, never before.
- It doesn't switch off after sliding the switch to the off position. This issue started yesterday. At beginning it switched off after few seconds, today it stay on for more than 2 minutes. There can be a voltage from the pin PB1 / VBAT_SENSE, if the pin is in an incorrect state.
Tibor