MembersPage/JohanEriksson/BigQ (2006-03-24 22:56:18)

Can anyone help me find out what value C12 should be?

xx1dg.png

Your load resistor is 100 Ohms. C12, in series with the 100 ohms wants to have an Xc of a lot less than 100 ohms (less than 10 ohms is good) at the baud that you will be using. Many similar circuits replace the capacitor with a short-circuit. The purpose of the capacitor is to reduce power consumption when there is no data flowing. If it were me, I would use a 10uF (because I have a lot of them in my parts bin!)although many different values would probably work well.

Thanks! I'll try a 10uF then, using 100nF now.. There must be something else wrong with the whole circuit (this image is just a piece of it) RXD and TXD connects to a PCA82C250 and then to CAN bus, it communicates but seems to lose data...

Try replacing c12 with a short circuit temporarily to see if that helps clear up the lost data problem.