roboRio limited to 8 Analog Inputs

[Joe Johnson]

Originally Posted by crake

There are several ways to extend the IO capabilities of roboRIO. The use of I2C and SPI (both options on the MXP connector as well) and communication protocols such as CAN give a lot of flexibility. It is an excellent opportunity for the development of "value-add" accessories for the control system.

Let me stipulate that I am finding this problem late and that I should have discovered it sooner. I assumed the new shiny FIRST controller would come with enough IO to support using all the great new sensors that are becoming available to FIRST teams.

Philosophically, we are planning to have a pot provide analog position for pretty much every motor we're using (except for the ones that drive the wheels, which use quad encoders, of course). Given this philosophy, it is really easy to use more than 8 Analog input channels.

Does anyone have a solid solution to this 8 ADC limitation?

I am trying to decide if I should use an Arduino and if so, then which one?

Is it legal to use a Leonardo powered off the roboRIO's USB? If so, does the roboRIO have drivers that recognize he Leonardo's USB Serial Port? I know others have suggested using I2C to communicate with the roboRIO, but it seems to me that it would be simpler if the roboRIO code can get to Leonardo's USB Serial Port.

Another option is the REV RIOduino. Has anyone had luck using this? We are using navX MXP card which may block this solution.

IF NOT ARDUINO, THEN WHAT?

I was thinking of this I2C Breakout Board from Adafruit? Thoughts?

My team needs a solid, reliable easily implemented solution without a lot of fuss and muss. I am sure that this is not a unique problem. If you have figured this out, please share.

Joe J.

P.S. I don't want to hijack this thread but if we go with the Adafruit ADC option, what about powering it? Can I take power from the MXP or do I need to go through a fused line from the PDP as R30, R37 & R42 (collectively) imply?

* Looking at the pinouts, it looks like the REV RIOduino passes through all the MXP signals so I may be able to plug the REV RIOduino into the roboRIO then plug the navX into the REV RIOduino. I have two concerns. First, will they even physically fit together (see photo attached). Second, both want to use the UART lines -- The roboRIO TX line is no problem as I can have them both listen without a conflict. But I will have to let one or the other use the roboRIO RX line. Never a dull momemt.