Compute Module • CM4 Breakout board RS485 issue

Hello

I wanted to use this channel to ask a question about my Raspberry Pi CM4 breakout board design.
- It uses a SP485 chip from MaxLinear to create a RS485 bus
- This SP485 chip is driven by a CH340E chip (USB -> serial)

With most devices this design works perfectly! But some other devices completely destroy the CM4 and the breakout board completely. Some devices causing this problem:
- A Solax Inverter
- A Sungrow EV charger (Sungrow inverters work perfectly)

When one of those devices (is connected to the RS485 port of my breakout board it destroys the PoE 5V power supply and the CM4 itself. The CM4 is also unusable in a working breakout board (it's completely fried)

Currently working perfectly (all connected to the same RS485 bus):
- Huawei inverters
- Goodwe inverters
- Solis inverters
- Heidelberg Chargers
- Phoenix Contacts Chargers
- Eastron energy meters

I place a picture of the Schematic of the RS485 design. I hope someone could help me find the mistake in my design.

Thank you!
Kind regards

Hacor

Statistics: Posted by hacor — Mon Feb 26, 2024 6:56 am

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