MD398 Reverse Engineering

Resources for the Tytera (TYT) MD398 (aka Radioddity GD-55).

General Information

The radio uses a vastly different design than the familiar MD380/MD390. It uses the AT1846S radio SoC. It is a familiar chip used in many Wouxun/Baofeng model, however to the key difference that this newer S series provides an IQ baseband interface.

It appears to be using an integrated ARM M7 built into the HR-C3000.

The programming cable is actually a common USB to TTL serial interface (not an actual USB device). It's still not impossible the radio could appear as a DFU usb device for upgrades however.

There is an unused ribbon connector on the front side of the mainboard.

Connector

The connector used is called M328+ (as used on the Motorola GP388 and others), sometimes also called M7. It is 40mm in length. The audio pinout appears to be identical to other radios using this connector. Two more pins are used for the programming port. Four more pins are unknown.

Boot Modes

Different boot modes seem to be available:

PTT	TOP SIDE BUTTON	BOTTOM SIDE BUTTON	EMERGENCY BUTTON	Function
X		X		Flip + Mirror screen
	X	X		??? Black screen no chime, upgrade mode?
		X	X	GPS Test mode