I’ve put information on how to communicate with the unit up here for future reference.

I found some information on an NI forum and on Matlab’s file exchange site.. The info on the NI site is a bit hard to read and not quite correct, so here’s a quick and clear rundown.

Serial Port Setup

If you’re using the USB cable, its actually just a virtual serial port, which will likely show up on your PC as COM1 to COM4. If you’re using the RS232 cable, then obviously you need a serial port on the PC. Either way, you need to set the serial port up for 2400 baud, 7 data bits, even parity, 1 stop bit, and no flow control.

Communication Overview

To read the temperatures from the unit, send this string over the serial port: “#001N\r\n”. Don’t include the quote marks. \r means the carriage return character (ASCII 13). \n means the newline character (ASCII 10). You’ll get back a string that follows this pattern: ” TTTTt TTTTtAB\r\n”. The first and second TTTTt groups represent the temperature and thermocouple type for the first and second thermocouple. The AB section is some miscellaneous information.

Temperature

The “TTTT” part will be a hexadecimal string representing the temperature in tenths of a degree Celcius. For example, ” 017A” represents 37.8 degrees Celcius. If the number is negative, it will start with a minus sign instead of a space. For example “-00C2″ means -19.4 degrees C.

Thermocouple Type

The “t” part represents the thermocouple type (set using the buttons on the HH506RA). The codes go as follows:

Miscellaneous Info

According to the document on the NI site, the “A” digit above represents Celcius/Fahrenheit while the “B” character represents battery. I’ve only ever seen them as 0 in my testing.

Example

Bringing it all together:
You send: “#001N\r\n”
You receive: “-00B20 02C1200\r\n”
Decoding: The first thermocouple is a type K that is reading -17.8 degrees C. The second thermocouple is a type T reading 70.5 degrees C.

Errors

If you send a bad command, you’ll get a a response of “Err\r\n”. I’ve found that to be a handy way to resynchronize communication in case something goes wrong. Just send “\r\n” and read for a response until you see “Err\r\n”. Once you get that response, you know the unit is ready to accept a command again.

Other Commands

The document on the NI forum has some additional details. For example, you can read the unit’s ID with the command “%IDR\r\n”. The ID is the set of digits you send in the read temperature command “#001N\r\n”. You can change the unit’s ID so that it responds to “#005N\r\n” by sending a command along the lines of “%001I005\r\n”. I don’t really see the point of this, so I haven’t bothered testing it. The unit can log data, which can then be read back with the command “#001S\r\n”.

The stats: 45 miles, average speed 13.1 mph (half a mph better than on last week’s 39 mile ride!), max speed 27.6 mph again (downhill of course), riding time 3h23, total time something like 4 hours.

Once you get off the bike path, people get a lot friendlier. I got a bunch of nods from other cyclists biking around Carlisle. While struggling my way up at 8-9 mph what the CRW site describes as a “mild rolling” hill I even got a big smile and a wave.

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