PIC to serial with visual basic

[mbw123]

Hello,

I am trying to hook up my PIC18F4550 to my serial port and send data using Visual Basic. The code for the PIC is below. I have a 22K resistor on the RX line of the PIC. The RTS and CTS lines I have working (thanks to skimask) but I can't seem to get the RX to work. The PC should transmit a "4" and the PIC should receive it and test its value. For visual basic the instruction I am using is: SerialPort.Write("4"). I believe I have the right baud and everything setup (9600) but I can't be sure (the rest is the default setup). Any help is appreciated! Thanks,

-Mike

Code on PIC:
------------------
Include "modedefs.bas"
define HSER_CLROERR 1
define HSER_RCSTA 90h
define HSER_BAUD 9600
define HSER_TXSTA 20h
define OSC 4

rts var porta.2
cts var portd.3
led var portd.2
rx var portc.7
OK var word

input rts
output cts
output led

ADCON1 = %00001111

low led : low cts

main:

while rts = 1

high cts
SERIN rx,N9600,OK
if ok = "4" then
high led
endif

wend

low cts

goto main

[skimask]

Code on PIC:
------------------
Include "modedefs.bas"
define HSER_CLROERR 1 : define HSER_RCSTA 90h : define HSER_BAUD 9600
define HSER_TXSTA 20h : define OSC 4 : rts var porta.2:cts var portd.3
led var portd.2 : rx var portc.7 : OK var word : input rts : output cts
output led : ADCON1=15 : low led : low cts
main:
while rts = 1
high cts : SERIN rx,N9600,OK
if ok = "4" then
high led
endif
wend
low cts
goto main

Why are you using the RTS & CTS lines? Just curious...I've never used them, never had a need, kinda complicates thing unneccesarily. Try this whole thing without the RTS and CTS lines. Set Windows to 'Handshaking-None' in the serial properties. See what happens then. Again, you're breaking it down, starting super-simple, then working your way up.

Another thing, you're using SERIN with HSER defines. Why?

And SERIN @ 4mhz isn't exactly reliable. Switch down to 2400 and see what happens.

You're also not using a MAX232. It should work with a PC using the inverted serial modes, but the voltage levels might not be high enough. You might end up using one. It's always worked for me, but you never know.

Incidentally, I got over 100 threads here on this site alone all about serial interfacing, PC's, visual basic, hyperterminal, etc.

[mbw123]

OK, thanks for the response.

I tried it without the RTS / CTS lines but it still didn't work.

Sorry about the HSER defines, I used them before and I forgot to get rid of them. Even without them and switching the baud rates, though, it still doesn't work.

"You're also not using a MAX232. It should work with a PC using the inverted serial modes, but the voltage levels might not be high enough. You might end up using one. It's always worked for me, but you never know."
Yeah, I may end up with a MAX232. I just want to avoid it if at all possible.

I really don't know where to go from here. Any help or suggestions?

Thanks.

-Mike

[skimask]

Did you switch to 2400 baud?
Did you read the manual where it says that 9600 baud might not be possible at 4mhz?

[mbw123]

Yeah, I switched it to 2400 baud rate and turned off the handshake. Maybe the visual basic code is wrong or the code on the PIC should be "if OK = 4" instead of 4 being in quotation marks. Or am I missing something that's staring me in the face?

Thanks for the help.

-Mike

[skimask]

Yeah, I switched it to 2400 baud rate and turned off the handshake. Maybe the visual basic code is wrong or the code on the PIC should be "if OK = 4" instead of 4 being in quotation marks. Or am I missing something that's staring me in the face?

Thanks for the help.

-Mike

Try this. It echo's everything you type on hyperterminal, but echo the same character 3 times and toggle the led every time you hit a key, that way you know it's really working..

Include "modedefs.bas"
DEFINE OSC 4
rx var portc.7 : output rx : tx var portc.6 : input tx
led var portd.2 : output led : serialdata var byte : ADCON1 = $F
main:
toggle led 'just show the program is running
serin rx , N2400 , serialdata
serout tx , n2400 , [ serialdata , serialdata , serialdata ]
goto main


Once again, you break it down, make it super simple, then build it back up...