old technology successfully talks to new
Thursday, December 27 2012
Now that I generally have the hardware working for the infrared range finder that I intend to use for measuring fuel levels, I had to write the software to support this new system. Today I continued tinkering with the code to run on the slave Arduino that will actually be controlling the analog-only IR range finder. I wanted to make it so that device could be monitored (via its serial port) with my Tandy Model 102, but to do that I had to make it not output data any faster than 19200 baud. I also had to make sure not to produce data any faster than its meagre buffer could handle. It didn't take much experimentation to realize that with old timey computer equipment like the Tandy Model 102, it's easy to overflow the serial buffer and start seeing weird things on screen. It bears mentioning that back in the time of classic personal computers, I never actually owned a computer capable of communicating over an RS-232 port; those sorts of features were too expensive for a budget funded primarily by saving my school lunch money.
But for the purposes of communicating with an Arduino board, it's easiest to use TTL levels instead of RS-232 levels. So I opened up the Tandy Model 102 and soldered some wires to its UART intercepting the serial data before it was converted away from TTL levels. I routed this data out to a new four-pin connector I built into its side and the Tandy Model 102 actually displayed useful data when I attached it to my new slave Arduino. There's a special form of æsthetic satisfaction that comes from successfully interfacing 30 year old technology to six year old technology for which a 16 letter German word may already have been coined.
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