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40 lines
2.0 KiB
40 lines
2.0 KiB
# MD398 Reverse Engineering
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Resources for the Tytera (TYT) MD398 (aka Radioddity GD-55).
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## General Information
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The radio uses a vastly different design than the familiar MD380/MD390. It uses the [AT1846S radio SoC](http://www.auctus.cn/enindex/ptshow.html?id=2).
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It is a familiar chip used in many Wouxun/Baofeng model, however to the key difference that this
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newer S series provides an IQ baseband interface.
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It appears to be using an integrated ARM M7 built into the HR-C3000?
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The programming cable is actually a common USB to TTL serial interface (**not** an actual USB device).
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It's still not impossible the radio could appear as a DFU usb device for upgrades however.
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There is an unused ribbon connector on the front side of the mainboard.
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## Connector
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The connector used is called _M328+_ (as used on the Motorola GP388 and others), sometimes also called M7. It is 40mm in length.
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The audio pinout appears to be identical to other radios using this connector. Two more pins are used for the programming port.
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Four more pins are unknown (but appear to be unrouted passed the ribbon on the front panel board).
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## Time Slots
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The radio CPS and firmware appear to only allow selecting Time Slot 1. It is possible to modify some xml to enable the CPS to program Time Slot 2.
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Doing that however, does not appear to change the behavior of the radio. The radio appears to transmit on both TDMA timeslots with duplicate packets,
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as a Tier I radio would (ie: ETSI 102 361-1 continuous transmission mode).
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## Boot Modes
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Different boot modes seem to be available:
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| PTT | TOP SIDE BUTTON | BOTTOM SIDE BUTTON | EMERGENCY BUTTON | Function |
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|:---:|:---------------:|:------------------:|:----------------:| -------- |
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| *X* | | *X* | | [Flip + Mirror screen](https://github.com/xSmurf/md398-re/blob/master/teardown/Display_InvertedMirrored.jpg) |
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| | *X* | *X* | | ??? Black screen no chime, upgrade mode? |
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| | | *X* | *X* | [GPS Test mode](https://github.com/xSmurf/md398-re/blob/master/teardown/GPS_TestMode.jpg) |
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