Hello all, I don't really have a problem, as I've resolved it already, but I do have a question.
When working with my keypad, I used whatever resistors happened to be laying around my bench (yeah, bad practice, I know =) for the pull-up resistors. They ranged from ~ 260 to ~1M in impedance. The keypad worked great with this setup (well, seemed to at least - I had an issue with the zero key not working =) but I couldn't upload any further sketches until all the pull-up resistors were removed (I got the 'out of sync' error that everyone else has been talking about). After some experimentation, I found that using any pull-up resistor (pulling up a pin to the 5v output on the arduino) rated less than 100KOhm caused the problem. Well, I didn't try, say, 90KOhm! ;D
Obviously, I replaced them all w/ 100K resistors and everything works fine, but why would this cause a problem? (Incidentally, doing this also caused my zero key to function again, heh.)
BTW, they were all connected to the analog inputs (as digital) and digital input 0.
There ya go - Digital pins 0 and 1 are used for serial TX and RX (or is that RX and TX?). A low value resistor placed there would screw up rs232 communications used for uploading.
Pins 0 and 1 can be used, but you need to be careful if you want to use them without interering with rs232 communictions, either sketch serial I/O or sketch uploads.
There ya go - Digital pins 0 and 1 are used for serial TX and RX (or is that RX and TX?). A low value resistor placed there would screw up rs232 communications used for uploading.
Pins 0 and 1 can be used, but you need to be careful if you want to use them without interering with rs232 communictions, either sketch serial I/O or sketch uploads.
-j
Ahh, excellent - thank you for the explanation. I presume b/c of the matrix nature of the keypad, and I had any row connected to a low-resistance pull-up, and a column connected to pin 0, it would have the same effect (which would seem like it kept happening no matter which pins I removed the pull-up from, pin 0 was connected to COL1).
Hmm. Between 4bit lcd, 4x3 keypad, and 4 motors, those pins start getting more and more scarce =)