Differernce between fullduplex serial RX and RxCheck

CRST1

I'm trying to receive bytes from a xbee in command mode. When I send the +++ command and check the fullduplex serial buffer with Buffer[1] := serial.rx and Buffer[2] := serial.rx I get "O" in buffer[1] and "K" in buffer[2]. If I use serial.rxcheck they show up as two "." The variable buffer is a long aray. Why do I get different results just by changing between RX and RxCheck? Rx returnes a byte and RxCheck returnes a byte as long as there is a byte in the buffer acording to the docs. I don't understand the difference. Can anyone help?

Thank you

Duane Degn

Rx waits for a character and RxCheck either returns the character or a -1 if the buffer is empty. It's a good idea to use a temporary long sized variable to catch the return value of RxCheck so it can be compared properly with -1 but when a valid character is received, it should be saved to a byte sized buffer element. All the string handling commands use byte buffers and trying to store characters in a buffer of longs is likely to cause you trouble.

I don't understand why RxCheck would be returning periods. You might want to post your code.

Negative ones will have the value 255 or $FF in all four bytes. When displayed with a TV or VGA object this shows up as the infinity symbol. I don't know what it looks like in a terminal window.

BTW, All Spin methods return a long. Often only the least significant byte is used but the return value is long sized.

CRST1

This code sends back two periods

            buffer[1] := 0
            buffer[2] := 0
            fds.rxflush
            fds.str(string("+++"))

            waitcnt(80000000+cnt)
            buffer[1] := fds.rxcheck
            buffer[2] := fds.rxcheck
            waitcnt(80000000+cnt)
            fds.str(string("atcn"))
            fds.tx($0D)
            waitcnt(800000+cnt)  
            fds.str(string("test"))  
            fds.tx(buffer[1])
            fds.tx(buffer[2])

This code sends back "OK"

            buffer[1] := 0
            buffer[2] := 0
            fds.rxflush
            fds.str(string("+++"))

            waitcnt(80000000+cnt)
            buffer[1] := fds.rx
            buffer[2] := fds.rx
            waitcnt(80000000+cnt)
            fds.str(string("atcn"))
            fds.tx($0D)
            waitcnt(800000+cnt)  
            fds.str(string("test"))  
            fds.tx(buffer[1])
            fds.tx(buffer[2])

Duane Degn

Add this code to the end of the second first set of code (and to the first second if you want).

           
            fds.tx(" ")
            fds.dec(buffer[1])  
            fds.tx(" ")
            fds.dec(buffer[2])

What's the output from the extra code?

Edit: The extra code needs to be added to the first set.

CRST1

I found out the problem. Went out cut grass and cooled off in pool and it came to me. I was using this board with another project that needed speed so it has a 6mhz crystal and the pll was set to 16. I guess fullduplexserial doesn't like the overclock. Changed it to pll8 and it now works. Thanks for the tips.