DATV-Express Project – February update report

[KenW6HHC]

The DATV-Express team ordered a small batch of bare PCB’s from a PCB fabricator in Oregon, named Sunstone. The blank boards arrived yesterday and will be used to check a few prototypes assemblies of the second layout. Art WA8RMC has already begun to hand-solder a “first-article“ prototype to see if the PCB board design works. Hand-soldering SMT parts requires uncommon skills (in my opinion), especially when fine-pitch SMT chips are being used. Our vision for the project is that when the design is proven, then larger batches of boards will be commercially assembled using “solder paste mask” techniques, “pick and place” robots, and soldering thermal reflow ovens.

Below is a photo of the "mostly bare" second-pass PCB layout with the power supply components already soldered in place.


When WA8RMC completes the hand-assembly of the first-article PCBA, he will first check out the five onboard power supplies. Then he will load onto the board some initial test code that has been supplied by Charles G4GUO to do simple tests of the FPGA…like blink some LEDs. If all goes well with Art’s electrical checkout, the first article prototype PCBA will be shipped across the pond to Charles in England to begin checking out the ported software. Charles has been updating the old FPGA code for this rev2 PCB. This will allow rapid evaluation of the new board when it arrives.

While waiting for the new board design to arrive, Charles has been looking at what might be done using the Raspberry-Pi (ARM based) single-board-computer and the MK808 media player (also ARM based) to interface with the DATV-Express board as an alternative to using a normal PC. With the help of Rob M0DTS, Charles has played with a modularised version of his DATV host software. It turns out that the Reed-Solomon FEC encoder software consumes a large portion of the ARM resources. Charles has tried porting the Reed-Solomon code to run inside our FPGA. This seems to work well. Also, we are lucky that Brian G4EWJ has written an optimised version of this module in ARM assembly language. His module uses about 1/4 of the processing that the G4GUO C module does. So we have managed to get the whole thing down from 60% to about 20%. There are further improvements that can be made.

Charles is hoping that the DATV-Express project can become a collaborative one at least as far as the software is concerned. "It may not be possible for everyone to hand solder SMD components these days but everyone can try to write some software. For small projects like this it is not that difficult and we all have to start somewhere".

"full speed ahead"...de Ken W6HHC

[KenW6HHC]

Art WA8RMC has been working hard on the new board. He has completed hand-soldering the components onto the "first article" DATV-Express PCBA that uses the project team's second layout. Art reports that all of the five power supplies are working correctly. The LED for power lights up and no IC's get hot (a good thing) and the Oscillator is running OK! At the end of a hard day of work, Art reported that he had not run the test software Charles G4GUO forwarded to him yet.

The "first article" PCBA is shown below fitting nicely inside a box chosen for the project.


I agree with G4GUO who has stated that the board looks better with its clothes on!

"full speed ahead"...de Ken W6HHC