Dynon says they’re going to add on-board data logging at some point, but until then, they only stream data out one of the RS-232 ports. So, I bought an inexpensive data logging device from SparkFun called OpenLog. At only $24.95, you can’t beat it. It takes a microSD card, so its pretty easy to transfer the log file to your computer. But, I didn’t realize that it was not RS-232 enabled, but was designed to log serial TTL data (for those non-EE’s out there, TTL is 0-5V whereas RS-232 uses +/- 12V). So, when I connected it up to one of they Dynon serial ports, I just got garbage. After a bit of head scratching, I finally realized that I needed a level converter to convert the Dynon RS-232 levels to TTL. The most common level converter used is the MAX232 chip. Since I only need the serial out line from the Dynon, I only sent those through the MAX232. Here’s a link for a MAX232 circuit (I used 1uF capacitors for all). I just used a small proto-board to mount the MAX232 chip as well as the OpenLog board. The input for this board were the serial out line from the Dynon, a 5V supply (I used a 7805 regulator to create the 5V supply from the 12V airplane voltage) and ground. To set the baud rate of the OpenLog, there’s a text file on the root of the SD card – I set it to 9600 and setup the com port on the Dynon to log everything. Once I put it back in the plane with the proper level converter, it worked great.
But, when I tried to import the log file into excel, I realized that I need to write some VB code to import it. Excel can import fixed-width text data like the Dyon spits out which is fine if you only log one thing (i.e. ADARHS, SYSTEM or EMS), but if you turn them all on, it sends out a line of EMS, then a line of SYSTEM then a line of ADARHS data. Each of those lines needs to be parsed differently. So, you need a bit of VB code to look at the line, identify which type of data it is, then parse it properly. I made a bit of VB code that does this and puts each data set into a different worksheet.
Here’s some pictures of the install. You can see the bare board. I put some heat-shrink over it and attached it with Velcro in a place under the panel that’s pretty easy to get to so I can remove the microSD card.
