Hi team,
Uses SCIA on the 28388D controlcard ( version B) to communicate with the PC serial port, configured as follows:
The Controlcard plugs directly into the customer's own interface board with a UT3232 chip-based SCI communication circuit (3.3V powered); the computer USB is connected to the chip via a USB-to-serial port. The output of the chip is connected to GPIO35, GPIO36 on the controlcard, and the pins are configured as SCIA_RX. SCIA_TX; receives signals from the computer serial debugger.
The 5-V power supply for the controlcard comes from the interface board, and the gnd signal is also connected to the gnd signal on the interface board at various points on the gold finger.
Checking the SCIA_RX signal from the UT3232 chip to the controcard (that is, the signal to be received by the 28388D) through the oscilloscope, there were some issues:
If the controlcard is not plugged into the interface board, the waveforms are basically same each time the same set of data is sent multiple times (5 bytes at a time) through the serial interface debug software, so the data is transmitted exactly the same.
However, when the SCIA_RX signal is tested in the same place after the controlcard is plugged in, the displayed waveform is much different each time the program is run on 28388 and different data is received each time. And actually the same data is sent.
The customer suspects it's related to the hardware. And the customer also attempts to power the UT3232 chip on the interface board with the 3.3-V voltage on the controlcard, but the problem remains.
Could you help check this issue? Thanks.
Best Regards,
Cherry