Serin and Serout problem

[rubisharmax]

Thanks Archangel, I changed the definitions as you said.

On the other hand, there's a weird problem again: I send a serial bytes of "50" and "55" from 12F675 to 18F2550. 18F2550 is supposed to take the serial data input and send it to PC via USB.

The transmitter code is as follows:

Include "modedefs.bas"  ' Include serial modes 

DEFINE OSC 4

CMCON = 7
ANSEL = 0

output GPIO.1
SO var GPIO.1                ' Define serial out pin
B0 Var byte

mainloop:
   pause 1
   B0=50
   Serout SO,N9600,[B0] ' Send character
   pause 1
   B0=55
   Serout SO,N9600,[B0] ' Send character
   Goto mainloop        ' Forever
 
End

And on the 18F2550, just trying to read serial input and then send it via USBOUT command:

DEFINE    OSC 48Include "modedefs.bas"
Buffer    VAR BYTE[1]
Cnt       VAR BYTE
counter   VAR WORD
B0        VAR BYTE


ADCON1 = 15               ' Set all I/Os to Digital      
CMCON = 7                 ' Disable Comparators
Cnt = 1


input PORTA.0 
SI var PORTA.0


USBInit                   ' Initialize USART

Loop2:
    Serin SI,N9600,B0
    Buffer(0)=B0  

Loop1: 
    USBService        
    USBOut 3, Buffer, Cnt, loop1
goto Loop2 ' Go and read serial input data again


end

The problem is: when I load the above code into 18F2550, PC doesn't see the virtual COM port. But when I change the code as follows, it works fine:

DEFINE    OSC 48Include "modedefs.bas"
Buffer    VAR BYTE[1]
Cnt       VAR BYTE
counter   VAR WORD
B0        VAR BYTE

ADCON1 = 15               ' Set all I/Os to Digital      
CMCON = 7                 ' Disable Comparators
Cnt = 1

input PORTA.0 
SI var PORTA.0

USBInit                   ' Initialize USART

Loop2:
    Serin SI,N9600,B0
    Buffer(0)=B0  

Loop1: 
    USBService        
    USBOut 3, Buffer, Cnt, loop1
goto Loop1 ' Send the same received serial data again and again to the PC

end

The problem is: I need to read each serial input data and send it to PC via USB on 18F2550. Tried loads of combinations but nothing worked except the latter code above, which sends the data received only once at the start of the program.

Any opinion to overcome this problem?

[vaporized]

Hello.
You have to service USB regularly (about 5ms max. between servicing) which the first 18F2550 program fails to do due to "goto Loop2" directing program to Serin. With Serin PIC just sits there waiting for serial data and can't do anything else (*1), like service USB, until the data arrives. And there are numeruos reasons for PICs not to get the data therefore just hanging on Serin.

*1 - o.k., not entirely true, PICs can run comparators, timers, send/receive serial data, etc. in background, depending on device's features.


You can try with Timeout parameter for Serin but I don't think it'll work as desired with such a short period as 5ms.
I would rather suggest you to employ 18F2550's UART for serial data reception. That way you can service USB while receiving data in background.
But keep in mind that UART size is 2 bytes so either make larger pause between data transmission so you have time to collect data from UART, send it to PC, and service USB; or use interrupts (mr. Darrel Taylor's Instant Interrupts are really great) in combination with (circular) buffer.
Another thing of importance when dealing with UART is that you have to switch to true mode (T9600 instead of N9600; pull-ups instead of pull-downs; data-line idles high)


Oh, one more thing - I see you're not using DEFINE OSCCAL in your 12F675 programs. I don't know if PBP3 (presuming that's your version) handles that differently than previous versions (PBP2.5 here) but please make sure and see about it in maual.