![dmr programming explained dmr programming explained](https://cdn.shopify.com/s/files/1/2779/0566/products/3_5e13b770-d03f-4b4d-af6d-3abadb88fc47_1200x1200.jpg)
#Dmr programming explained full#
One MMDVM DMR hotspot can operate either in simplex mode, where a single time slot is used for BS downlink and uplink, or in full duplex mode, where both time slots are used and can carry voice transmissions. Besides these advantages, the TDMA access scheme requires very strict timing for base station access, and the mobile station (MS) needs to be time synchronized to the BS and transmit within a specific window of time in order to be received in its own timeslot and avoid interfering with the other timeslot where a different radio transmission can occur independently. More than that, the DMR protocol offers call routing between logical channels called talk groups, as well as direct calls between two DMR radios identified by a unique ID.
![dmr programming explained dmr programming explained](https://img.staticbg.com/images/oaupload/banggood/images/B0/3B/92f30484-3e4c-4379-b4ae-34ac17226cb1.jpg)
This means that each base station (BS) can carry two radio conversations simultaneously in a single 12.5 kHz channnel, effectively offering double the capacity compared to a single FM 12.5 kHz repeater. Some technical details about the ETSI DMR standards and the MMDVM implementation of these standards will follow.ĭMR is a radio standard which implements a double timeslot time division multiple access scheme (TDMA). With these hard problems already solved, there remained the issue of transmitting the modulated samples through a SDR device.
#Dmr programming explained serial#
This fork of MMDVM ( MMDVM-SDR) by Peter Rakesh had already solved the issue of serial port communication with MMDVMHost by using a virtual serial port, enabling it to run on a regular Linux computer instead of a microcontroller and use different audio sample input/out rather then the microcontroller ADC/DAC. Luckily, I wasn't the only one targetting this functionality, and there was at least one port of MMDVM to GNU/Linux. This is why I began to think some time ago if it would not be possible to adapt such an SDR as a digital voice hotspot (with DMR as a target mode, since I already have DMR radios). Some of us, including me, use a SDR device for most of their amateur radio activities, and want to adapt their SDR to a multitude of tasks, to avoid using multiple hardware device types for the same job. There are two main software components involved: MMDVM, which runs on a microcontroller board and MMDVMHost which runs on a GNU/Linux host computer, usually something like a Raspberry Pi board and handles connectivity to the network and the main scheduling logic. Using it and some custom hardware you can access DMR, D-Star, YSF and other voice networks worldwide. MMDVM is a popular software created by Jonathan Naylor G4KLX which powers the multitude of digital voice hotspots or digital voice repeaters so common today. Using GNU Radio and a SDR device as a digital voice hotspot with MMDVM supported modes like DMR, D-Star, YSF