Let's Make Robots!

Question from Someone who is Supposed to be Answering Questions

rik and I were talking about this a few days ago and it crossed my mind again today.

What are your thoughts on sending serial data from one pic (say picaxe or arduino) to another pic and if you should have a current-limiting resistor in series between them. In my case, both chips are running off of the same 5v regulated power supply.

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On my robot the 2 PICs are just wired together, without a resistor, works fine. Agree with Tinhead.

I googled and googled this one and of course, simply found a ton of posts about the RS232 vs. TTL power issues. --It was not real easy to find search terms to find pic to pic info. I assumed the same, all of my stuff is direct wired and I have had no/few problems. I just got to thinking about this and thought now that Walter is getting close to "all put together" and up-and-running, if this were an issue I had missed, I should stop and fix it now. Seems like we are good to go.


The only two things I can see as concerns are that your logic levels are compatible (range of voltages defined as logical HIGH and LOW), and that each output has adequate current source to sink into each input.

Most likely, you are good to go.

Also, I figure you already knew that, but I posted for the benefit of anyone who doesn't. ; j

You beat me to the source sink related issue that I have always been concerned about, I like throwing a small1/8 or 1/4 watt 1k in series just in case.

I must confess, that I've killed a microcontroller and a Roomba main board, by mistakenly connecting TX and TX together. A simple serial resistor would have avoid this desaster. Only the UART pins have been damaged the rest seems to be ok.