Gender Bender Activated

OK, today I put in place the new gender-bender and null-modem adapter that I got from Radio Shack the other day. Here's what the setup looks like currently:


(The "yo" on the display is an acknowledgment that a line of data was received from the GPS.) And here is the new logic-level serial waveform output by the level shifter:


The rise time is noticeably shorter, it is now measured to be about 1.3 us on average, whereas previously I eyeballed it to be about 4 us or so. Hopefully this will cut down on serial glitches! Unless they're due to buffer overflows. Facebook friend Kragen suggested I also try cutting down the baud rate. It's currently 115,200 baud. I will do that if necessary, but first I want to see if this change helps. I need to collect a new data set, and perhaps while I'm at it, I will also instrument the firmware to look for checksum errors in the lines received from the GPS.

OK, I successfully modified the firmware to check the NMEA checksums in the lines received from the GPS before passing them on to the PC over the wireless connection. If there are errors, they are reported to STDOUT as well as to the server via Wi-Fi. I also made a video on my digital camera to demonstrate how to start up the whole system; I will post it on YouTube later. I think I will leave the current run going over the weekend; we can collect a whole 3-day dataset for Gordon to process later with his Java code. I will email him now to give him a heads-up about that.

A few more photos, just for fun:

1. Scope trace showing about a half-second worth of stuff. Purple: PPS pulse. Cyan: Level-shifted (logic-level) serial data from GPS. White: CTS from Wi-Fi and TX to Wi-Fi.
   
   
2. Server display showing (a) Wi-Fi diagnostic STDOUT-->COM terminal window used during startup (top left), (b) Main window (middle), (c) Message stream window (upper right), (d) Auxilliary I/O window (lower left), (e) Application data stream window (lower right), (f) Data stream transcript file viewer window (back).
   
   
3. FPGA board diagnostics. (a) Nios 2 terminal window (STDOUT stream via JTAG UART via USB, right), (b) Terminal transcript file viewer window (left).
   
   
4. Firmware code in Nios 2 IDE. Top of main routine.
   

Cheerio!