RB_STM32_DVM - FAQ
(Frequently Asked Questions)
- Where can I find documentation on this product?
Version 1 (Green Board) Schematic & Board Layout
Version 2 (Red Board) Schematic & Board Layout
- Is there any MORE documentation?
Not at this time. I *barely* had enough time between building boards to create this FAQ page.
If folks would to contribute any connection diagrams, I will gladly share them or link to them from this FAQ page.
- Connection Diagrams / Write-ups:
- Will your board work as a single radio hotspot like the ZumSpot board or is it only for repeater?
Yes. It will work simplex. I know LOTS of folks who are doing that very thing.
- Is there Firmware on the board when it ships?
Yes. I load the most current version of the firmware on the board during testing. All boards are ON-AIR tested before shipment.
The firmware I currently load has RSSI and the COS input enabled. (more on these options below.)
- Why does the firmware on my board look REAL old?
The version date of all the software does not change as often as one would think. Jonathan G4KLX only "bumps" the software date when he feels he has crossed a milestone or when he feels there has been enough change to the codebase.
The "build date" is the date the firmware was actually compiled. This date can be found in the DVM "sign on" message in the MMDVMHost log.
In the PiStar image, this log can be found in /var/log/pi-star
- How do I update the firmware?
Here is a link to some notes that Steve N4IRS came up with for uploading new firmware to the board if necessary:
- Where do I find the newest firmware?
The pre-built binary files can be found here:
- Is there firmware for your board that supports the NXDN protocol?
YES!! Here is a link to firmware that includes the NXDN protocol. ALL versions of the STM32-DVM will "DO" NXDN, even though there is no indicator LED for it. (YET)
- My board won't go into / stay in BOOT LOADER mode, and thus I can't upload new firmware. Any suggestions?
Depending on the age of your board, pull-up R2 may or may not be populated. If it is not, you might try populating it with a 2.2kO
to 100KO resistor. According to the specs on the processor a pull-up is not a necessity, however I started populating R2 with a
10k resistor and it has seemingly made it WAY easier to get the processor into boot mode.
- Why are there no header pins soldered in JP1?
I don't stuff a header in JP1 as it would interfere with the case. (pins stick up too high)
My usual method of shorting the pads is to place a pair of tweezers in the two holes and apply power. Once you are in boot mode (three LEDs on) you can remove the tweezers/jumper and the board will remain in boot mode.
- Why doesn't the RSSI input work?
There is a known issue with the RSSI input.
This issue has now been fixed thanks to Spencer N4NQV. The new firmware image is available at the repository directory listed above.
- Where do I connect the COS pin?
The COS input on the STM32 is *NOT* a traditional "carrier active" input, but rather a "DISABLE" pin. This pin is designed to be used with an outboard CTCSS decoder, or similar, that would tell the DVM to "turn off" when is an analog QSO in progress.
This input is active LOW, meaning if it's pulled to ground, the DVM will go into inhibit mode. ("LED" flashes rapidly)
- My Transmit/Receive doesn't work. Why?
There are two things that can kill the digital receive/transmit: Audio level and polarity. In the RX chain, we can easily get the level set correctly with the on-board "clip light." That only leaves polarity. Transmit/receive polarity is set in the host software running on the Raspberry Pi or equivalent.
If you are running Pi-Star, simply navigate to http://pi-star/admin/expert/ Part of the way down you'll see a section that says "modem." Under that you'll see TXInvert and RXInvert. Toggle RXInvert from a "1" to "0" or vice-versa.
- I don't have time to watch the video above on adjusting the RX audio. What is the correct procedure?
This procedure assumes you have raw, unsquelched, discriminator noise applied to the RXA input. (no signal)
The correct method to adjust the RX audio chain is to turn the Multi-turn gain pot (R20) down the whole way. (CCW until it starts clicking - no more than 25 turns) With the gain set to unity (gain pot at minimum) turn the single turn pot (R3) up until the CLIP light comes on, then back it off slightly until the CLIP LED just goes out. If you can't get the CLIP light to come on with the single turn pot at 'ON'(full CW), then leave R3 pot wide open and start turning the multi-turn gain pot CW until the CLIP light comes on, then back if off slightly.
If you can't get the clip light to come on with BOTH pots fully CW, there is something wrong with the discriminator input to the board!!
- Can I connect an OLED display and where?
Absolutely!! On Version 1&2 (Green and Red) boards these connections will need to be soldered onto the pins of the 40 pin Raspberry Pi mating connector. On upcoming boards there will be a row of PCB pads added for this purpose. See this page for more information:
- Can I connect a NEXTION display and where?
A NEXTION display requires a comm. port. Unfortunately we use the only comm. port on the Raspberry pi's 40 pin interface to talk to the PiHat. This being the case, you *can* add a NEXTION serial display, but you'll need to use a USB to TTL converter plugged into the USB port of the Pi. Again, this is the hardware solution, you'll need to do some digging as to how to configure Pi-Star to talk to the correct (USB based) comm. port. I will revise this answer if a "how-to" page is found.
Official Product of Scott Zimmerman / Repeater Builder
Inspired from a similar design: github.com/wojciechk8/MMDVM_pog
Low-pass filter design by SQ6POG
Images property of Repeater Builder.
Logo Design by Elisha Zimmerman KB9WCX
HTML June 17, 2017 - N3XCC