DATV-Express Project – April update report

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KenW6HHC
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Joined: Mon Jun 01, 2009 4:20 pm

DATV-Express Project – April update report

Post by KenW6HHC » Thu May 01, 2014 9:42 pm

First, the BAD News - In April, Charles G4GUO managed to get the Raspberry-PI software working as shown in the “Raspberry-Pi Development-phase03” block diagram in the March report. He was able to get it work up to 8 MSymb/sec….BUT it would only run for a few seconds before the software froze. There were two major obstacles. First, the way Raspberry-PI handles USB traffic is to do a “lot of writing to memory” and this consumed CPU-cycles. The CPU consumption on RPI was running maybe 40-80% depending on the Symbol-Rate used. Second, any GUI movement would spike the CPU-cycles to 100% and everything stopped. Charles’ conclusion was the Raspberry-Pi single-core-ARM processor running at 800 MHz does not have enough CPU-horsepower for our project!

Now, the GOOD News – Charles tried using an RKM MK802iv “mini-PC” that is sold on Amazon for turning television sets without internet access into “smart TV’s” that could surf the internet and watch movies via Netflix download or streaming video, etc. See Fig01 below for a size comparison of this “mini-PC’ unit from RikoMagic (RKM).

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Figure 1 - Size comparison of quadcore-ARM MK802iv with a deck of cards.

Rob MØDTS had been successfully using the dualcore-ARM model MK808 unit to run the DigiLite board. The newer model MK802iv unit purchased by Charles has a quadcore-ARM processor that runs at 1.6 GHz!! Just a day or two of tweaking buffers (etc.) allowed Charles to get the DATV-Express software running on PicUntu linux with the DATV-Express board.

For price comparison; a Raspberry-Pi with power-unit, a few cables, and plastic case costs about $59 on Amazon. The MK802iv with power-unit, a few cables, and plastic case costs Ken W6HHC $72 on Amazon in USA (shipping was free, too).

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Figure 2 – A Block Diagram of typical MK802iv set-up for transmitting DVB-S

Charles was able to push the MK802iv unit to drive the DATV-Express board at 12 MSymb/s with DVB-S protocol. A block diagram of the MK802iv DVB-S test set-up is shown in Fig02. The block diagram components shown in dashed-lines (Display, keyboard, etc.) are only needed to set-up and configure the software. The dashed-line components are not actually needed to run the transmitter....just a real SPST switch to act as PTT.

Ken W6HHC spent about a week “polishing” the rough-edges for installing the DATV-Express software on the MK802iv. Ken explains that the MK802iv can be purchased in two flavors. One flavor comes running Android “Jelly Beans” OS. The second flavor comes running Linux OS (called the LE edition). In both cases, the user needs to re-flash-the MK802iv unit to put a different Operating System called PicUntu v4.5 (a light-weight variety of ubuntu linux) onto the unit. All of the software flashing tools and PicUntu v4.5 are free to download on the internet…and takes maybe 15 minutes perform the re-flashing step.

The plans for the team now are for Charles G4GUO to continue testing and refining the DATV-Express software for the MK802iv, Ken W6HHC will begin drafting a “standalone” User Guide version to support future MK802iv users, and Art WA8RMC will be demonstrating DATV-Express at the Dayton HamConvention in May.

“full speed ahead”…de Ken W6HHC
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