Interrupt Driven Serial Input using DT_Ints?

[circuitpro]

Can someone please point me to a link or example of how to make an interrupt-driven serial input buffer (hserin) for use with DT_Ints? I have had an interrupt jump to and receive an entire string of characters, but I've got too much going on for that, and will have to receive the string one character at a time, and put the command together when there's time. Any example would get me started. Thanks

[Darrel Taylor]

Here's one where I modified Joe's serial backback program for use with DT_INTS.

http://www.picbasic.co.uk/forum/show...8336#post28336

[circuitpro]

Thanks very much, Darrel!

[circuitpro]

I am having some kind of issue getting these two uarts set up right. I'm using a PIC18F6722 running at 40MHz. UART1 runs perfectly fine at 115K, but UART2 just can't hack it. (If I lower the baudrate to 57600, it works fine). Besides setting the pin directions, I am using the setup resulting from the PIC Multicalc as follows:

'EUSART 1 (RS422 LINK)
DEFINE HSER1_RCSTA 90h
DEFINE HSER1_TXSTA 24h
DEFINE HSER1_CLROERR 1
DEFINE HSER1_SPBRG 86
SPBRGH1 = 0
BAUDCON1.3 = 1

'EUSART 2 (RS485 LINK)
DEFINE HSER2_RCSTA 90h
DEFINE HSER2_TXSTA 24h
DEFINE HSER2_CLROERR 1
DEFINE HSER2_SPBRG 86
SPBRGH2 = 0
BAUDCON2.3 = 1

I am not doing anything fancy, just trying to get both ports to transmit and receive at 115k - one at a time. No interrupts, nothing fancy.

Can anyone tell me why HSERIN2 fails to work when HSERIN1 works at this baudrate?

[Darrel Taylor]

I'm not sure how you got EUSART1 working.

There are no HSER1_ defines.
They are just HSER_ for the first EUSART, and HSER2_ for the second.

[circuitpro]

The datasheet for the pic just refers to TCSTAx, and at first I was setting them up with HSER_RCSTA and HSER2_RCSTA, but out of mass frustration, thought I would see if it should really be HSER1 & HSER2. (Once again, it's logical, but wrong!)

Do you see any reason uart2 isn't working at 115k?

[Darrel Taylor]

Do you see any reason uart2 isn't working at 115k?

From a software point of view, no.
PBP does exactly the same thing with both USARTS, which looks like this ...
Blue is EUSART1.
Green is EUSART2.

000000                01183     ORG RESET_ORG               ; Reset vector at 0
000000 EF13 F000      01193         goto    INIT            ; Finish initialization
                      02343 HSEROUT CLRWDT?                 ; Keep Watchdog clear
000004 0004               M         clrwdt
000006 A89E           02344         btfss   PIR, TXIF       ; Wait till ready
000008 D7FD           02345         bra     HSEROUT
00000A 6EAD           02369         movwf   TXREG           ; Send the char
00000C 80D8           02370         bsf     STATUS, C       ; Set no timeout for Serout2mod
00000E EF10 F000      02371         goto    DUNN            ; That's it
                      02567 HSEROUT2 CLRWDT?                ; Keep Watchdog clear
000012 0004               M         clrwdt
000014 A8A4           02568         btfss   PIR3, TX2IF     ; Wait till ready
000016 D7FD           02569         bra     HSEROUT2
000018 6E6D           02593         movwf   TXREG2          ; Send the char
00001A 80D8           02594         bsf     STATUS, C       ; Set no timeout for Serout2mod
00001C EF10 F000      02595         goto    DUNN            ; That's it
000020 0100           07799 DUNN    movlb   0               ; 1 Reset banks to 0
000022 0004               M         clrwdt
000024 0012           07801         return                  ; 2 Done
000026                07815 INIT
000026 0E56               M         movlw   low (86)
000028 6EAF               M         movwf   SPBRG
00002A 0E24               M         movlw   low (24h)
00002C 6EAC               M         movwf   TXSTA
00002E 0E90               M         movlw   low (90h)
000030 6EAB               M         movwf   RCSTA
000032 0E56               M         movlw   low (86)
000034 6E6F               M         movwf   SPBRG2
000036 0E24               M         movlw   low (24h)
000038 6E6C               M         movwf   TXSTA2
00003A 0E90               M         movlw   low (90h)
00003C 6E6B               M         movwf   RCSTA2
00003E                07852 main
00003E 6A7F               M         clrf    SPBRGH1
000040 867E               M         bsf     BAUDCON1, 003h
000042 6A7D               M         clrf    SPBRGH2
000044 867C               M         bsf     BAUDCON2, 003h
000046 0E00               M         movlw   000h
000048 DFDD               M         rcall   HSEROUT
00004A 0E00               M         movlw   000h
00004C DFE2               M         rcall   HSEROUT2

Which leaves hardware.
Something with the 18F6722? (doubtfull). Nothing in the errata sheet.
Extra capacitance on the PCB or serial cable. Bad cable?
<strike>Not enough capacitance on the MAX232?</strike> OOPS, RS422/RS485 ... no MAX232

Hard to tell.

[circuitpro]

That's very helpful - Thanks! It's going directly to a 75ALS180 (RS485), and the signal looks good on a scope, so I'll do some more testing - focusing on hardware now.