Topics

FM/NXDN Mode and older MMDVM modems


Jonathan Naylor
 

Hi Folks

I see a lot of comments about the MMDVM not supporting various hardware with the new FM work. I think I need to point some things out:

1. The developers don't have access to all of the hardware that is out there. We can only support what we have, and even then it isn't easy. Ultimately if your hardware was created by G9BF, then it is G9BFs responsibility to support it. If we can make sure it runs correctly then we'll try to do so, but we make no guarantees. The most common quality modem hardware is provided by KI6ZUM, N3XCC (Repeater Builder), BI7JTA, and DF2ET. This list is not exhaustive, but these represent good quality boards and you can reasonably expect them to work. However see note 2 below.

2. With the additional work on the MMDVM, we are finding that some of the older MMDVM hardware no longer has enough processing power to run it. This first came up with NXDN mode, and this is now showing itself with the new FM mode. Geoffrey F4FXL had to do some amazing optimisations in order to get the standalone FM mode to run on the Arduino Due, but there is no way that this platform will support the use of external audio (i.e. Echolink). This comment also applies to other boards, typically ARM M4 boards with clock speeds lower than 180 MHz. This unfortunately applies to Arduino Due based interfaces, Repeater Builder V1 and V2 boards, SP6POG boards, and many no-name boards that are sourced from China via eBay.

If you are buying a new MMDVM modem board and you aren't sure what processor that it uses, ask the seller. If it's less than a 180 MHz ARM M4 and the seller claims that it supports FM or NXDN mode, don't believe them. Better, buy your board from a reputable seller, you may be paying more, but you'll be getting guaranteed hardware with a good chance that it will work with future upgrades.

Jonathan  G4KLX


Razvan M
 

Hello Jonathan,

I partially disagree with  "...developers don't have access to all of the hardware that is out there...". 99% of the boards are based on the same STM32F series (105 or 446). The POG version has been sold (manufactured) in thousands of units. N3XCC's green & red boards are an improvement of the SQ6POG's concept, are of superior quality and I have two of them in use (check the footer on RB website). The latest boards from BI7JTA are a rip off (*cough* decent clones?!) of the N3XCC red board.

Now, with Arduino and STM32F105 hitting the wall, the problem will be sourcing a quality (>180 MHz) board, especially if you live in EU. Scott's boards are great but they don't come cheap, not to mention the customs fees and transit time. BI7JTA's are 30% cheaper but again I would like to know a shop within the EU for a decent and affordable board.

Anybody?

Regards,
Razvan YO6NAM


Jonathan Naylor
 

The F103 support is completely different from that used for the F446 so they’re completely different as far as the MMDVM is concerned. So your comment is nonsense.



On Monday, June 1, 2020, 18:26, Razvan M <yo6nam@...> wrote:

Hello Jonathan,

I partially disagree with  "...developers don't have access to all of the hardware that is out there...". 99% of the boards are based on the same STM32F series (105 or 446). The POG version has been sold (manufactured) in thousands of units. N3XCC's green & red boards are an improvement of the SQ6POG's concept, are of superior quality and I have two of them in use (check the footer on RB website). The latest boards from BI7JTA are a rip off (*cough* decent clones?!) of the N3XCC red board.

Now, with Arduino and STM32F105 hitting the wall, the problem will be sourcing a quality (>180 MHz) board, especially if you live in EU. Scott's boards are great but they don't come cheap, not to mention the customs fees and transit time. BI7JTA's are 30% cheaper but again I would like to know a shop within the EU for a decent and affordable board.

Anybody?

Regards,
Razvan YO6NAM


Razvan M
 

Someone is having a bad day...
Who said anything about F103? Have you read at least half of my nonsense comment?


Shawn Chain
 

In MMDVM firmware, F103/F105 shares the same code base while F44x/F7xx shares another same code.
I will trying to take a look into that issue as I have a F103 board to test.

BTW, This is an open-source project, please contribute your code or knowledge, but not complain.

Cheers,

BG5HHP


Razvan M
 

Shaw,

Thanks for the clarification and intention to have a look.

I just made a comment and asked a question, that's no reason for some of you to get uptight, unless is it against the rules to disagree.
I'll STFU but the question remains, if anybody cares to recommend a board.

Cheers!