Servo - June 2011

The last item was to configure the SPI settings from the terminal — perhaps the world’s tiniest and simplest user interface. I created a small set of commands to set the various operating modes and printed out a very short menu to the terminal. This is shown in Figure 12. Upon reset, the menu is displayed and the program waits until you enter a command, which either sets the mode of the SPI bus or initiates operation. The monitoring proceeds until the user resets the processor (through a power cycle).

Future Expansion FIGURE 11.

I2C functionality could be added to the system quite easily by tweaking the hardware for the SPI port to include appropriate pull-ups and updating the software to read the I2C protocol. The prototype boards allow easy rip-up and replace so this would not be a big deal.

The current processor only has 256 bytes of RAM, but other devices are available up to 1,024 bytes and an internal oscillator of 32 MHz. Moving into the PIC 18F family or perhaps an Arduino would allow for a much more powerful system.

So, that concludes the SPI monitor project. Full details are available on the website if you want to construct your own. There is plenty of opportunity for improvement if you have any ideas. SV