The Mini-HotSpot Board

Almost two years after its introduction, the most popular board still is our Mini-Hotspot board. Initially designed to only handle Simplex links (we simplified the original dual-processor design based on the assumption that most people would not need the second processor for repeater mode) so we could have a smaller board, the current firmware happily handles Duplex mode on this board wtithout problems.

With the new DUTCH*Star HSA designed and almost ready for production, we did not expect customers to still order this board... but they do, and they do it a lot!

So, much to our own surprise, we proudly present the new version of our Mini-Hotspot board, the "Revision C", also known as the "Blue Board".

Not many things have changed since we updated the original board to fix some initial errors, and added D-COS.  We made the board a little smaller after we cleaned up the placement of parts, for example. The most important change in this revision is, that it is now operating in the so-called "V5" mode, which means that it does forward the RSSI information from the modem chip to the processor chip, which subsequently can send it to the PC for further usage.

If you'd like to know more about it, you can download the schematics here, which also includes the BOM (Bill Of Materials, also known as the Parts List) and the parts placement drawing.

The PCB production files are available for those who want to make a board for themselves and/or some friends. Send us an email and let us know what you want to do, and we will try to help you out!

The Construction and Reference Manual (version 2.00) describes how to build your board into a working Mini-HotSpot system. It also contains a parts list in case you want to buy your own parts, as well as a detailed parts placement drawing so you can easily what-goes-where.

You can order this board, a complete parts kit and even a ready-to-use built&tested unit in our Web Shop. which is also the place to go to order our firmware for it if no ready-to-use unit is needed. A pre-made Radio Cable is also available, this cable will connect the board to most modern transceivers that feature a PS/2-style ("MiniDIN-6") port labeled "data", "packet" or "tnc".

The people at the Yahoo! GMSK_DV_NODE group will be more than happy to help you with any problems you might run into- after all, it is the same board that is run by many others on that group.



Back in 2009, when the GMSK Node Adapter was introduced, the Mini-Hotspot board also started its history.  Below are some older announcements regarding this board and its various incarnations.

If you don't need the standalone repeater mode (which is the case if you use the board with the HotSpot software), then you can use the new Mini-HotSpot board, which simply is a smaller, trimmed-down version of the original Node Adapter design. It does not have the second processor and its supporting circuits, and, therefore, cannot be used in standalone-repeater mode.

Designed by Mark Phillips G7LTT, the original Mini-HotSpot PCB only measured 2.5 x 2.75 inches, and ran the original Version 4.XX family of firmware, written by Satoshi Yasuda JK1ZRW. It is no longer being offered for sale as the PCB had some design errors. 

A direct result from the co-operation between Mark and Fred van Kempen PA4YBR, the new version of the Mini-HotSpot board is a little larger than the original version (3.6 x 2.1 inches) and now uses a somewhat cleaner placement of the various LED's, jumpers and connectors, at the cost of a board that is slightly larger. 


After some discussion on the Yahoo! group, it was requested that Andy G4ZSM's Digital COS circuit be added to our board. This circuit uses the RSSI value generated by the CMX589A modem chip to determine if there is a valid signal being received or not, and this result is then used as a COS signal to the board.

Especially with systems that have to deal with both analog (FM Voice) as well as digital (GMSK D-STAR) signals, using the GMSK quality indicator gives better results for determining whether to enter analog or digital mode. Dual-mode repeaters will obviously benefit from this !

The new Mini-HotSpot PCB with the Digital COS added to it (and some other minor cleanups, as set out for Rev.A01.) You can see the extra RSSI LED's (the yellow ones).. during reception, these LEDs will indicate the relative signal strength. If the signal strength exceeds a level set by the user, the circuit will raise the COS line, and the green LED will light, indicating we have a valid signal at hand.

This signal adds another jumper switch (SW2); it selects between Analog COS (the signal from the radio, polarity being selected by SW1 and SW3) or Digital COS, which is our new signal.

All this fun obviously requires space on the PCB, so we had to make it a little larger. Not a lot, only about 10mm or so; its length remained the same. We could have muddled with smaller trimpots, but to keep things clean and simple, we decided to just make the board larger- this also allowed us to place the extra LEDs, and add the jumper.


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