MMDVM Firmware, why update? How to update!

Have you heard "ham radio" people talk about updating the firmware of the MMDVM boards and wonder, should you?

The general opinion is "Always move up to the latest level", which is fine for early adopters that really know what they are doing or pretend to at the very least.

An experienced voice will say "Stick with the version that is working and only move up if there is a feature you really need or want".

That is the best advice we can give, stick with what it working and ALWAYS read the firmware build notes as to what it delivers before applying it. 

Good news! The MMDVM firmware is open source! 

Unlike many radios, you can read about all aspects of the code at:  https://github.com/juribeparada/MMDVM_HS/

Where can you see the latest notes on MMDVM Firmware?
https://github.com/juribeparada/MMDVM_HS/releases

Here is the build log to see what each version delivers:


v1.4.12

• Frequency restrictions to avoid satellite interference. Please avoid the following ranges: 145.8-146.0 MHz and 435-438 MHz, otherwise, the firmware will not start. Please see: http://www.arrl.org/news/digital-mobile-radio-hotspots-may-be-interfering-with-satellite-uplinks-amsat-reports
• Fix RSSI bug in duplex mode
• P25 RX logic rewrite
• Enable debug messages for simplex boards
• Add new Interrupt Counter Test Mode (requires MMDVMCal >= 20181104). Useful for board diagnostics (TCXO, ADF7021 connections, etc).
• Makefile option for USB firmware without bootloader (only custom compilation)
• Minor bug fixes

v1.4.8

• Fix for bug with the new Raspberry Pi 3 B+, when using an MMDVM_HS with USB

v1.4.7

• Fix for clock drift between radio and duplex HS (See Steve K2GOG's article)

v1.4.6

• Fix D-Star reliability with low RSSI signals (transmission lost recovery)
• Fix for missing POCSAG start tone and incomplete messages
• Receiver gain options (only custom firmware builds)
• Additional NanoDV boards support

v1.4.3

• RAM memory optimization
• Fix small bugs

v1.4.1

• Add support for POCSAG
• Fix LEDs bug and minor bugs (thanks Flo DF2ET)

v1.3.7

• Reducing YSF, P25 and NXDN buffer sizes to fix RAM limit bug in duplex mode
• Add binary firmware support for generic MMDVM_HS boards with serial interface

 v1.3.6  (Very stable, most boards shipped with this)

• More space for ring buffers
• Pseudo random fill instead of 1.2 kHz fill for DMR DMO

 v1.3.3

• Support for MMDVMCal
• Deviation adjustment for each mode in MMDVM.ini
• Default RSSI support for MMDVM_HS_Hat
• Support for MMDVM_HS_DUAL_HAT board
• Support for Nano DV board
• Optimizing program size

IMPORTANT NOTE: Please set all TXLevel parameters to 50 % in MMDVM.ini in order to use default deviation levels.

What MMDVM boards are we talking about?

You need to know which board you own!

Look it up on google and match the image with what you have.  Do not just assume saying "Version 1.0" is the same for everyone.

Also, you will need to know what TCXO also known as a "crystal" is on your board. (14.xxxx or 12.xxxx MHz)

Once you know that you can flash your board from the PiStar command line ( "http://{address of your PiStar}:2222 login" with pi-star as the user name, if you did not change the password the default is raspberry )

• ZUMspot RPi board
  sudo pistar-zumspotflash rpi
• ZUMSpot duplex board conected to GPIO
  sudo pistar-zumspotflash rpi_duplex
• ZUMspot USB dongle
  sudo pistar-zumspotflash usb
• ZUMspot Libre Kit or generic MMDVM_HS board with USB
  sudo pistar-zumspotflash libre
• MMDVM_HS_Hat board (14.7456MHz TCXO)
  sudo pistar-mmdvmhshatflash hs_hat
• HS_DUAL_HAT board (14.7456MHz TCXO)
  sudo pistar-mmdvmhshatflash hs_dual_hat
• MMDVM_HS_Hat board (12.288MHz TCXO)
  sudo pistar-mmdvmhshatflash hs_hat-12mhz
• HS_DUAL_HAT board (12.288MHz TCXO)
  sudo pistar-mmdvmhshatflash hs_dual_hat-12mhz
• Nano hotSPOT board
  sudo pistar-nanohsflash nano_hs
• NanoDV NPi board
  sudo pistar-nanodvflash pi
• NanoDV USB board
  sudo pistar-nanodvflash usb

An example: Updating a Chinese JumboSPOT"

So this is the board I (Joe N1JTA) bought from eBay awhile back:

I then soldered on the pins to enable FW update (Please see my past article "MMDVM JumboSPOT board: Mods you may need"

Also you can see the TCXO at X1 which under magnification shows it the 14.7456MHz TCXO. Thus this board is the "MMDVM_HS_Hat board (14.7456MHz TCXO)"

Before doing anything backup your PiStar settings via: http://pi-star.local/admin/config_backup.php

It's actually quite painless, that is if you don't mind the good old command line! First login in to your PiStar HotSpot's terminal: http://pi-star.local:2222 aka http://{your pistar ip address}:2222

Recall that the Default User name: pi-star and Default Password: raspberry that is if you have not changed it ( I recommend changing the password )

Login then run:

sudo pistar-mmdvmhshatflash hs_hat

Yes it's that easy! The command will find the latest build of hs_hat download it and apply it to your JumboSPOT.

Please note you MUST have connected the Firmware pins of your JumboSPOT to your Raspberry Pi for the flash utility to work. That is the above command will fail if your board does not have it's FW pins connected ( please see MMDVM JumboSPOT Mod you should know )

Advanced: Build FW from source, the easy way!

The normal WARNING! you are responsible for your hardware! Don't do this if you are afraid of messing up your critical infrastructure. Well if you mess up you can always flash with the commands above to recover.

https://www.df2et.de/mmdvm_hs_builder/

Please note that this site only will build the generic hs_hat for single and dual time slots. Now you can use this handy web page to chose what features you want to turn on or off!

A must have for me is "Constant Service LED once repeater is running" so once Pi-Star comes online the modem will NOT blink it's green LED. If you work near your hotspot that dang blinking light can be annoying.

Once you chose all the features you want in your FW then click "Submit" when done it will open a download. You can save a copy on your PC if you like. Under the download section it will provide you a link to the bin file. Thus at the Pi-Star command line you can do the following:

pi-star@dual-mmdvm(ro):~$ rpi-rw
pi-star@dual-mmdvm(rw):~$ wget http://www.df2et.de/mmdvm_hs_builder/5b7a1697910c8/MMDVM_HS/bin/mmdvm_f1.bin

You should see a message about ‘mmdvm_f1.bin’ saved

pi-star@dual-mmdvm(rw):~$ sudo pistar-mmdvmhshatflash-custom
mmdvm_f1.bin

Make sure pi-star is in write mode. Not only will the download fail but the fw flash will also fail.

What did you think?

Constructive comments are always welcome. Thanks! 

Improving the TCXO for Duplex MMDVM Hotspots

Various MMDVM hotspot devices have been on the market for about 3 years now and only recently have there been duplex ones available, which create more capability but with more complexity.

Proper passive and/or active cooling is a must when it comes to proper
operation of the duplex hotspot devices currently on the market.
Pictured device was constructed by Steve K2GOG

This HVDN article will explore making some thermal improvements to the duplex MMDVM boards that have become widely available over the past few months and are replacing many of the older hotspot devices available over the past few years.

The TCXO is one of if not the most critical part on the duplex
 hotspot device that creates user satisfaction

Problems and Corrections For Duplex MMDVM Hotspot Operation

TDMA based modes such as DMR are very reliant upon very stable time references. In order to create the simultaneous TS1 and TS2 capability, the TCXO needs to be extremely stable and quality components are only part of the equation.

If a Raspberry Pi 3 or 3B+ is to be used with many of the duplex hotspots, its important to do the following:

More Power: Ensure you are using a 5V 2.5A continuous or higher power source. Your RPI3B+ draws enough current and when coupled with the duplex board creates a higher load.  You need ample enough current to ensure stable operation.

Remove Heat: Placement of the MCU on the Raspberry Pi can create enough heat that will rise to the bottom of the Duplex MMDVM board which can influence its stability. You must use a heat synch or heat spreader accordingly to keep temperatures stable and as low as possible. These techniques are often known as passive cooling.

Move Heat: If it is not possible to remove heat, you can move it by using active cooling through the use of a small fan.  If choosing this route for heat management, consider the current impact this may have on your power supply.

Passive cooling through the use of self adhesive heat
spreaders on the bottom of the MMDVM duplex board

Appropriate Enclosure:  Do not choose to mount your assembled RPI3B plus MMDVM Duplex hotspot in a plastic, Plexiglas or 3-D printed enclosure. This enclosed and insulated enclosure may limit the life of your hot spot as well as impact its overall performance. Consider a metal or open frame construction if there is no option for active cooling available.

Proper RF Grounding & Shielding: Proper selection of antennas and installation of the SMA connectors is important to top performance of your hotspot.  Selecting the correct frequency that will best perform with your antennas and characteristics of your MMDVM device are important. HVDN recommends using frequencies in the lowest part of the 70cm allocation in your country for transmit as well as receive with appropriate spacing and separation.

Inside of Steve K2GOG's passively cooled duplex hotspot. Changes include extended SMA antenna
connectors to pass through the top of metal vented enclosure, passive heat spreaders under the
TCXO and directly above where the MCU is directly underneath the MMDVM board.

Correct Firmware: The development teams that create the hardware and software constantly make revisions based on user feedback. As of the August 22nd 2018 revision, improvements for TCXO management have been included in the firmware and it is advised for users to upgrade to atleast FW. 1.4.7 to take advantage of this. Here is a good article on how to update the firmware by Joe N1JTA

If you choose to use the Raspberry Pi Zero series of single board computer, many of the heat related issues are not much of an issue.   There is only one duplex board available that has a similar footprint as the RPIZW and is made by N5BOC and is available for purchase on Tindie, but HVDN has not yet been lucky enough to get one just yet for testing.

The N5BOC  duplex board is the smallest and most stable hotspot
device on the market capable of dual time slot operation

To learn more about some of what has been discussed in this article, here are some additional links:

https://github.com/juribeparada/MMDVM_HS

https://github.com/g4klx/MMDVM

https://github.com/nano-mmdvm/Duplex_hotSPOT

https://www.tindie.com/products/dave31418/mmdvm-duplex-in-pi-zero-form-factor/

https://www.facebook.com/groups/213986962488948/search/?query=tcxo 

https://www.makeuseof.com/tag/keep-raspberry-pi-cool/

https://www.digikey.com/product-detail/en/taitien/TXJTPDSANF-14.745600/1664-1281-1-ND/6126591

https://github.com/rogerclarkmelbourne?tab=repositories&type=fork

https://www.amazon.com/gp/product/B0755S5J3G/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B07217N5LS/ref=oh_aui_detailpage_o05_s01?ie=UTF8&psc=1