I’m currently helping a couple of engineering students finish a senior project that didn’t get finished last year. Long story… Anyway, it’s a bicycle brake tester being built for Paul Components. The mechanical design is great, but they had trouble with the electronics.
Part of those electronics involved writing numbers to a pair of Sparkfun 7-segment displays. There’s a lot of discussion on the Sparkfun board about these: apparently they’re difficult. I had some issues making them work —baud rate, for example, which should be set to 9600 in setup() not 2400 as stated in some references— but it’s relatively straightforward once those issues are straightened out. Here’s my code, in hopes that it’ll be helpful to anyone else trying to write to several 7-segment displays simultaneously.
The serial TX line (second pin given in the SoftwareSerial declaration) should be connected to the RX pin on the corresponding Sparkfun breakout board; the RX line in the SoftwareSerial declaration should be left unconnected.
For more detail: Driving multiple Sparkfun 7-segment displays with an Arduino