Re: External Power - What is possible?

I have developed an avionics application for the M5Stack. Using a proto module, I built a 5V regulator powered by a 14 Volt electrical system, and made a simple RS232 receiver to extract air data.

I connected directly into the 5V pin on the main connector.

Everything works fine.

The RS485 interface design for the COMMU appears to be wrong. As shown, the transmit data (TXD) is used to enable/disable the driver on the DE/RE pins, while the driver data input, DI is permanently strapped low.

This means that sending data will drive a 'one' or float the line, but never drive a 'zero'.

The correct implementation should be TXD connected to the DI pin and a third signal used to control the DE/RE pins.

Since there is no third signal available, this design is fundamentally broken and won't interoperate with my existing systems.

V