ThumbDV™ – Model A

Beginning with orders placed after July 9th, 2015 a new revision of the ThumbDV™ will be shipped.

The only difference between the original ThumbDV™ and the new model ‘A’ is that the USB serial port will now operate at 460800 baud instead of 230400 baud.  Programs like WinDV, DummyRepeater, and AMBEserver have been updated  to support both baud rates.  It may take a few days for DummyRepeater to be pushed out with the change.

There is no change for D-STAR applications except selecting the faster baud rate.

Note: At this time we recommend using DummyRepeater with ‘AMBEserver -n’ (-n is for new baud rate) for best performance with model ‘A’.

The latest source for AMBEserver can be found at GitHub.

Why are we changing the baud rate?

NW Digital Radio has been working with some OEM customers who will be integrating the ThumbDV™ into their products, including DMR based systems, and their existing programs use the higher baud rate to communicate with the AMBE3000 chip.  Moving to the higher rate allows these customers to more quickly integrate these systems.

Will older ThumbDV™ devices continue to be supported and sold?

NW Digital Radio will support ThumbDV™ both original and ‘A’ models.

Our inventory of original ThumbDV™ dongles sold out on the same day that the new model ‘A’ was delivered from the Washington State assembly house.  We do not plan to manufacture any additional 230400 baud ‘original’ ThumbDV™ dongles.

All new orders will receive the ThumbDV™ model ‘A’

What about the PiDV™ (DV3000)?

There are no plans to move the PiDV™ (GPIO) to a different baud rate.  However, it is relatively easy for the user to modify the boards to support additional baud rates through trace cutting and jumpers. [Note: the PiDV™ is not currently being produced or sold. Please use the ThumbDV™.  If you need a large quantity of PiDV™, 50 or more, contact sales.]

There has been some confusion, hopefully the following will help clear it up.

The ability to do vocoding for DMR, D-STAR, Fusion, P25 Phase 2, etc. is built into the AMBE 3000 chip.  The new Model ‘A’ only changes the baud rate that the serial port passes packets to and from the chip.  It does not change any other capability between the original and Model ‘A’.

The 230400 baud rate is sufficient for all of these protocols.  The OEM(s) we are working with are swapping out another USB AMBE-3000 device with the ThumbDV. That other device was strapped at 460800 and they just want to swap it out.

It doesn’t make sense for us to make 2 models, one strapped at 230400 and one strapped at 460800 so we are now making all units strapped at the higher baud rate.

There is no secret, hidden, message here.  It’s a simple baud rate change that we wanted customers to be aware of, nothing more.

Here is the math:

The fastest input from one voice stream is 128 Kbps (8000 samples per second at 16 bits). So 230 kbps in is more than sufficient. The fastest rate out is full rate at 7.2kbps, DMR, Fusion half rate,  and D-STAR are at 3.6kbps. (This is for encoding, reverse for decoding.) There is only one packet stream, so you don’t get any doubling of these numbers.

There is literally nothing different than the selected baud rate, implemented in an update printed circuit board that changes what lines are strapped down.

The AMBE 3000 chip provides the vocoding, and only the vocoding.  The various protocols embed the vocoding in their respective data streams.  The ‘devices’ (e.g. AMBE 3000 boards, dongles, etc.) are not involved in the actual protocols, only in turning voice into AMBE and AMBE into voice.

Please view John Speaks on DV Modes at MicroHams to see how digital voice systems are built up.