2PX I2C Pullup?

Shredder

I have a BS2PX on a Board of Education Development Board (Serial Version).
I am getting ready to connect my Matrix Orbital GLK12232-25-WBL thru the I2C bus.
I am also going to use this I2C expansion board.. www.roboticsconnection.com/catalog/item/988888/2309377.htm

Should I be using a pullup ressistor? 4.7K?
I ask because I already had a UM-FPu V2 connected thru the I2C expansion board and it all seemed to work fine.

Harbor

You should always use a pull-up on the data line of I2C, Shredder. In any application it's possible to get apparent success on a signal line without the pull-up, but the circuit won't be reliable. So put one in even if the current way seems to work.

It is possible that the expansion board you're using provides the pull-up of course. I don't have time to read the specs, but with the nominal value of a pull-up most designers choose, it won't do any harm to add your own pull-up at the Stamp pin. [noparse][[/noparse]And yes, 4.7k is a good value.]

Shredder

Thanks for the info! I am new to all this and figuring it out as I go.

And after closer indpection last night, It turns out I had 4.7K pullups on the little circuit board I made to mount the UM-FPu on. So I did have pullups.

I cut them off, and mounted them on the expansion board in the places that it had for putting pullups..

Thanks again for helping clear things up [noparse]:)[/noparse]

Harbor

You're welcome. Glad we could help.