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Tool/software:
Hi experts,
We encounter a SPI issue when implementing DMUX of the psu chip: the signal on SDO pin is always 0 when we enabled DMUX and NCS is high. Our SPI bus has one master (TMS570LS1224) and two slaves (TPS65381A-Q1 and MCP3208).
We have tried to tap the SDO pin from the MCP3028 as following, point 1 and point 2 when DMUX enabled only. (as there is a resistor between MCP3208 and TMS570)
At point 1: The SPI log shows the MISO data are correct.
At point 2: The SPI log shows the MISO data are always 0 when NCS is high.
Looks the MISO data are holding 0 by TPS65381 SDO pin when DMUX are enabled and NCS is high.
The weird thing is why AMUX enabled doesn't cause this issue?
Our connection for your reference: SDO pin from TPS65381A is connected to TMS570 directly, while SDO from MCP3208 has a 1K resistor between TMS570.
As we noticed the following note in TPS datasheet. What's your thought of our hardware implementation, is there an issue? Or how can we resolve it by software? Thank you very much.
Please refer this thread we raise against TMS570.
Best regards
Longhua