16f877 rs232 problem and some Matlab

strumpfm · Joined: 23 Nov 2003 Posts: 7 Location: Seattle, WA

I'm using a 7 segment display, so i just threw that led object into visio quickly and didn't think about it. I have been setting MCLR to Vdd to run the PIC, and I am using a power supply, not a battery (again, visio). I have been running it at 5 V, but I can try it at 6 also. For the compiler I'm using the PCW compiler IDE version 3.36, and using MPLAB IDE version 6.30, and a Picstart programmer. My led's were working before with previous programs, so I know that it is wired properly. Everything in the circuit worked before except for the crystal. Hmm...

Mike

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

If nothing works, question everything.

1. Check your power supply and ground connections.
Verify that your +5v is really +5v.
2. Check that your programmer is really programming the chip,
and especially the config bits.
3. Look at the .HEX file, and closely examine the config bits
at the end of the file. Compare them to the chart in the
data sheet. (Hint: The two config bytes in the .HEX file
are swapped, compared to the register bit diagram in the
data sheet).
4. Get a new PIC chip.
5. Get a new crystal.
6. Verify all part values. Are the caps really 22 pf. Check them
with a capacitance meter. (Commonly available on most low cost
DMM meters).

Basic idea: Question all premises. All.

Guest · Posted: Tue Nov 25, 2003 2:09 pm

Well, sorry to post so much. I got a 20MHz oscillator (the sort with 4 pins: tri-state, gnd, vdd, and out), and that seems to be pretty accurate. The led's flash and I get a data stream on the Tx pin, but the voltage isn't nearly high enough. I probably got two bad crystals yesterday. Now all I need is a max232 chip and maybe I can make some sort of circuit diagram that could come in handy to someone else.

Mike