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DMR

OpenGD77 Project

OpenGD77 is a very exciting and active DMR radio project. This project involves hacking the inexpensive Radioddity GD77 dual band DMR handheld and its associated customer programming software (CPS). The core group of developers who are working on OpenGD77 are Roger VK3KYY, Kai DG4KLU, Jason VK7ZJA, Alex DL4LEX, Daniel F1RMB, and Colin G4EML.

Apparently the radio hardware in the GD77 is pretty decent and, it turns out, very hackable. Thanks to the persistence and hard work of the developers and the activity of a community of users and testers, development of the OpenGD77 firmware is currently very rapid. Imagine a cheap DMR radio that has functions designed specifically for amateur radio use, not just features suited for the commercial market. For example: DMR Tier 2 compatibility, direct talkgroup (TG) entry, monitoring on both timeslots or match (“promiscuous” or digital monitor mode), persistent TG assignment across timeslot and channel changes, excellent scanning speed and features, smart use of TG lists, and on and on.

And a very cool feature of the OpenGD77 firmware is that the radio can be used as a hotspot! When connected to a raspberry pi running pi-star, the radio is controlled by pi-star and MMDVM and becomes the RF portion of your hotspot. Because it can operate at higher power than traditional MMDVM hats, this makes it a potential long-range hotspot. And because the RF hardware of the GD77 is better than that of the MMDVM hats, it does not need to be setup with offsets for RX or TX to operate well (like many cheap jumbospots do).

To load and fully access the new features of the OpenGD77 firmware, one needs to use the “Community CPS” also being developed by the same team. This version of the CPS allows loading of the OpenGD77 firmware and access to new features such as capturing screengrabs from the radio, calibrating the TX power, backing up the radio EEPROM, FLASH, MCU, and calibration. Also, this CPS allows the use of 80 channel zones (rather than the normal 16).

A group of us in the OpenGD77 forum has also been working to update the User Guide document with the latest features and functions. You can access the most recent version of the User Guide here (link will always point to the most recent version).

The main place to learn about and keep up with the OpenGD77 development is on the OpenGD77 forum. Also, connect to OpenGD77 Talkgroup 98977 on BrandMeister. In addition, you can access the latest builds of the OpenGD77 firmware in this GitHub repository of Roger Clark. To download the latest Community CPS, go to this GitHub repository of Roger’s.



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