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.

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