Thank you for your advice! I have studied SPI for this project with this stage:
- Aruidno UNO - UNO : SPI worked & SCK, MOSI, MISO, SSN waveform checked as well
- UNO - GP22 : not worked
- UNO - GP22 physical connection & using UNO-UNO SPI code : not worked
- UNO - UNO physical connection & using UNO-GP22 SPI code : worked
The problem is that even the inner function, SPI.transfer does not work for UNO-GP22. The connection is right, and I used the same code as you uploaded(GitHub - leokoppel/GP22: An Arduino library for the Acam GP22 Time-to-Digital Converter).
And I just found that for the case of the 3 above, SSN, SCK, MOSI waveform works well, but there is no signal from MISO pin. I have already checked the soldered status. Do you guys have any idea?