Pic Max233a connection

[Monkeyman87]

Does anybody have any suggestions on how to connect a pic16f628 to a max233a and the max 233a to my pc's serial port. The pic will be converting analog data and sending it through the serial line async to the max233a then to the pc. I have tried connecting the pic's tx line to the max ttl input and connecting the pc to the rs232 output but I just get a bunch of gibberish on the pc. Thanks in advance

 

[e]

sounds like you have it hooked up right if you are getting something, remember that it has to be ascii in most cases to be readable.
see Nigel's tutorials I think there is rs232 there

 

[Nigel Goodwin]

Yes, my tutorials show how to do RS232, and the later analogue tutorial shows how to transfer analogue readings via RS232 as well.

 

[falleafd]

You can also reference to Tiny bootloader to get the hardware modules.

Software of PIC is shown clearly on nigel's tutorial.
Software on PC can be found at www.lvr.com

 

[Monkeyman87]

I'm using the pic's hardware usart to do the comm on the pic side but I tested the rs232 output of the max233 while the ttl input was tied to either 5v or gnd. The results: tied to ground i get approx 9v tied to 5v i get approx. .5v no negative output for the rs232 logic high. Is this normal? It doesn't seem right to me but this is what I get. Any suggestions? Thanks

 

[Nigel Goodwin]

I'm using the pic's hardware usart to do the comm on the pic side but I tested the rs232 output of the max233 while the ttl input was tied to either 5v or gnd. The results: tied to ground i get approx 9v tied to 5v i get approx. .5v no negative output for the rs232 logic high. Is this normal? It doesn't seem right to me but this is what I get. Any suggestions? Thanks

No, the RS232 side should switch from about +10V to -10V, if it's not going negative it sounds like you have something connected incorrectly.

 

[Monkeyman87]

Ok this is how its connected. I have 5v to vcc, 0v to gnd, the pic tx line rb2 to ttl2 in, and the line going to the pc is ttl1out. There is a 10uf cap across vcc and gnd. No other caps as the 233a doesn't need them. I don't know where my connections are wrong. Could the chip be bad?

 

[Andy_123]

With MAX233 you must jumper together:
Both C2+ pins 15+11
Both C2- pins 10+16
Both V- pins 12+17

See datasheet for example.

 

[Monkeyman87]

Thanks that explains alot. Pretty obvious if I would have looked a little closer. My transmit works now thanks again