Set up an MMDVM repeater without a network connection/host

[electric2u]

Which own did you get the stm32 DVM Nanopi or the stm32 DVM Pihat? I don't really understand the different, they seam like the same thing I'm slowly learning, then I'll order my parts once I fully understand, what I'm about to do.
Then its how to set up the IC-121 radio

 

[knockoffham]

Which own did you get the stm32 DVM Nanopi or the stm32 DVM Pihat? I don't really understand the different, they seam like the same thing I'm slowly learning, then I'll order my parts once I fully understand, what I'm about to do.
Then its how to set up the IC-121 radio

I don’t even have one yet, since I’m trying to figure out what would be easiest to use. But I’m leaning towards one of the Pi hat ones and then controlling it externally.

 

[knockoffham]

Which own did you get the stm32 DVM Nanopi or the stm32 DVM Pihat? I don't really understand the different, they seam like the same thing I'm slowly learning, then I'll order my parts once I fully understand, what I'm about to do.
Then its how to set up the IC-121 radio

Did you get yours running without a network?

 

[kayn1n32008]

Did you ever get it to work? I'm looking at doing the same thing. I have two ic-121s that I would like to create a stand alone DMR repeater no network. Dumb question can a DMR radio get repeated though a analog repeater and work?

No. The reason for this, is that the repeater has to supply the timing reference to define the timeslots and keep the user radios transmitting on the correct time slot.

When you key a DMR radio in duplex mode(where the transmit and receive frequencies are not the same) the radio is expecting a specific response to set up the time reference, so the radio knows when to start transmitting on the correct timeslot, from the repeater. An analogue repeater doesn't provide the response.

 

[knockoffham]

No. The reason for this, is that the repeater has to supply the timing reference to define the timeslots and keep the user radios transmitting on the correct time slot.

When you key a DMR radio in duplex mode(where the transmit and receive frequencies are not the same) the radio is expecting a specific response to set up the time reference, so the radio knows when to start transmitting on the correct timeslot, from the repeater. An analogue repeater doesn't provide the response.

Yes, I know this. That is why I am looking to use an MMDVM. Just without networking.
P25 however will actually work as a straight pass through on 2 analog radios if you get the audio levels just perfect.

 

[kayn1n32008]

Yes, I know this. That is why I am looking to use an MMDVM. Just without networking.

You will need a Pi to control the MMDVM, but it should not need to be connected to the internet once you have it set up

P25 however will actually work as a straight pass through on 2 analog radios if you get the audio levels just perfect.

Correct. It needs to be 'flat audio' not emphasized/de-emphasized audio. Keep in mind, you don't get any error correction when it passes through the repeater. A proper P25(Quantar or Codan MT-4E for example) repeater applies forward error correction, before retransmitting.

 

[knockoffham]

You will need a Pi to control the MMDVM, but it should not need to be connected to the internet once you have it set up

Correct. It needs to be 'flat audio' not emphasized/de-emphasized audio. Keep in mind, you don't get any error correction when it passes through the repeater. A proper P25(Quantar or Codan MT-4E for example) repeater applies forward error correction, before retransmitting.

Yep. I’m just hoping it can be done without a Pi, all I need is the right serial commands since MMDVM is all TTL serial

 

[tweiss3]

I understand what your intent is, but why are you so opposed to using a RPi? My understanding you need a host. the MMDVM is just the modem with RF on board. You are looking for the STM32, which is using the MMDVM modem, but designed to connect to repeaters. You still need either a computer or RPi for the host. Repeater Builder STM32-DVM

 

[knockoffham]

I understand what your intent is, but why are you so opposed to using a RPi? My understanding you need a host. the MMDVM is just the modem with RF on board. You are looking for the STM32, which is using the MMDVM modem, but designed to connect to repeaters. You still need either a computer or RPi for the host. Repeater Builder STM32-DVM

Ease of setup, portability, and just a fun experiment nobody seems to have done or at least documented

 

[kayn1n32008]

Ease of setup, portability, and just a fun experiment nobody seems to have done or at least documented

The host has a bunch of functions. One is to apply the forward error correction to the incoming data before its retransmitted.

It's also sets up the time sync to define the timeslots for the subscribers. It's not just getting data to flow from one radio to the other. The software running on the computer or Pi does all this using the modem.

In a way, the radios interact with the repeater, beyond just keying up like a conventional P25 radio, or a NXDN radio because the DMR radios are using TDMA.

When you press the PTT, the radio sends a series of wake up packets to the repeater, and is expecting a specific response from the repeater, before the radio begins sending data. Also keep in mind,

Could it be done by an arduino? Maybe? I don't know.

 

[knockoffham]

The host has a bunch of functions. One is to apply the forward error correction to the incoming data before its retransmitted.

It's also sets up the time sync to define the timeslots for the subscribers. It's not just getting data to flow from one radio to the other. The software running on the computer or Pi does all this using the modem.

In a way, the radios interact with the repeater, beyond just keying up like a conventional P25 radio, or a NXDN radio because the DMR radios are using TDMA.

When you press the PTT, the radio sends a series of wake up packets to the repeater, and is expecting a specific response from the repeater, before the radio begins sending data. Also keep in mind,

Could it be done by an arduino? Maybe? I don't know.

It’s the modem that does all that work. So I am looking to set up a modem that runs itself without a host needing it to turn on, assign color code, etc. I am aware of how DMR works with TDMA and once started on a project to do this before I knew of MMDVM but just decided it was too hard before I got very far.
And yeah you can use an Arduino, one of the more advanced ones anyway. They did at one point support DVM host firmware on the Arduino Due (and might still), but it did need an interface board which seems to no longer exist, which as far as I remember was just filtering and perhaps some op amps. All the modem boards are STM32 based so they could be hacked as long as they have programming pins accessible and are not read only. I was just hoping to avoid the massive project of going though source code and creating a custom fork that does not involve a “server”/“host” to control the modem since I just lack the time or motivation at the moment.

 

[Project25_MASTR]

It’s the modem that does all that work. So I am looking to set up a modem that runs itself without a host needing it to turn on, assign color code, etc. I am aware of how DMR works with TDMA and once started on a project to do this before I knew of MMDVM but just decided it was too hard before I got very far.
And yeah you can use an Arduino, one of the more advanced ones anyway. They did at one point support DVM host firmware on the Arduino Due (and might still), but it did need an interface board which seems to no longer exist, which as far as I remember was just filtering and perhaps some op amps. All the modem boards are STM32 based so they could be hacked as long as they have programming pins accessible and are not read only. I was just hoping to avoid the massive project of going though source code and creating a custom fork that does not involve a “server”/“host” to control the modem since I just lack the time or motivation at the moment.

DVM Project is a fork which already accomplishes the need to not utilize a server (well it's localhost in practice).

What you are wanting is to not have a host involved at all, correct?

 

[knockoffham]

DVM Project is a fork which already accomplishes the need to not utilize a server (well it's localhost in practice).

What you are wanting is to not have a host involved at all, correct?

Correct

 

[KN6SIO]

Correct

The host is the actual brain and logic function layer that works on conjunction with the modem. It isn't as simple as "hey, do this if receive that" like an Arduino would do. It needs to actually process in real time.

The modem doesn't actually do all that on it's own, it's still driven by host software.

Think of the modem like a keyboard. Sure, it has all the keys, but without a user pressing on them (the host) it won't do anything. If the host wasn't needed, it wouldn't be included. Host is there for more than just adding network.




For what you want, you can use DVMhost, on a pi. Network not needed for localized repeater function. Set the config, run the program, done. Can even set it to start when powered on, so it's as simple as tying it into power along with the rest of the portable setup, and flip the switch, bam, everything will boot up. If it doesn't, you can check the logs on the pi as to why.

It can be configured for "set it and forget it".

I do this often myself.

An Arduino is simply not what you'd be able to use.


None of the software is even remotely designed not capable of running in the way you want, not without complete ground up retooling.

Even the firmware on the modem requires host in order to do anything.

 

[knockoffham]

The host is the actual brain and logic function layer that works on conjunction with the modem. It isn't as simple as "hey, do this if receive that" like an Arduino would do. It needs to actually process in real time.

The modem doesn't actually do all that on it's own, it's still driven by host software.

Think of the modem like a keyboard. Sure, it has all the keys, but without a user pressing on them (the host) it won't do anything. If the host wasn't needed, it wouldn't be included. Host is there for more than just adding network.




For what you want, you can use DVMhost, on a pi. Network not needed for localized repeater function. Set the config, run the program, done. Can even set it to start when powered on, so it's as simple as tying it into power along with the rest of the portable setup, and flip the switch, bam, everything will boot up. If it doesn't, you can check the logs on the pi as to why.

It can be configured for "set it and forget it".

I do this often myself.

An Arduino is simply not what you'd be able to use.


None of the software is even remotely designed not capable of running in the way you want, not without complete ground up retooling.

Even the firmware on the modem requires host in order to do anything.

Cool. From the limited 'MMDVM standard' documentation I could find, it looked like it was all just serial commands sent to the modem telling it how to be configured, something I could easily do with an Arduino. But the newest documentation I could find was from like 20156. I did not know there was complicated processing on the host side. I thought the modem sent the received digital data stream to the host via serial and if there was to be no networking the host could just ignore it. I tried to take the MMDVM firmware from GitHub, and modify it to run host-less on an Arduino Due, but after a couple days decided that it was just too much of an undertaking for me. Thanks