PIC 18F8760 Specific RS232 routine

by Jim at JPes

Starting with an unknown board
https://plus.google.com/u/0/+JamesNewton/posts/CKnu7yU9BGv
found by a local electronics recycler:
http://www.ourplanetrecycling.com/

This board is from a muscle stimulant system for post surgery recovery, manufactured by/for, and distributed by VQ Orthocare. There are newer units to replace it now. This unit is the SurgiStim3, and has been replaced with SurgiStim4. If you power it up with >5V, and ground the third pin from the left of J2, the unit powers up, shows an opening screen from half a second or so, then goes to a screen that says your authorized time of use has elapsed and to put it in the cradle overnight for updates.

• U2 (Flash memory) is a 2Mb memory arranged as 262,144 bytes.
• U3 may be 5V regulator.
• U4 is a High Voltage EL Driver IC from SuperTex (Now owned by Microchip) for the LCD Backlight.
• U5 is a Maxim DS1307 64x8 real-time clock.
• U6 had different numbers between the boards (LCX16245 and LVC16245A), but both are 16-bit bidirectional bus transceivers with 5-volt tolerant I/O.
• U7 may be a 5V-3V converter/regulator.
• PZ1 is a Mallory-Sonalert AST200 3-volt, 85dB piezo transducer. Resonant frequency is 2730 +/- 500Hz.

It appears that J1 is an ICSP connector. A quick run through with the meter indicates that the pinout of the connector is ...
Pin 1 is VDD (5V),
Pin 2 is Clock,
Pin 3 is Data,
Pin 4 is Reset, and
Pin 5 is Ground.

I have verified that the PIC can indeed be erased and programmed via a PICKit3

{ed: this might be a great board for the Minimal Controller Idea }

 ;================================================
 ;
 ; Simple code example to test port pin and USART
 ; ;================================================
 ; Configuration
 list        p=18F8720
 #include    P18F8720.INC

 CONFIG OSC       = HS
 CONFIG WDT       = OFF
 CONFIG LVP       = OFF
 CONFIG DEBUG     = OFF

 ;================================================
 ; Variables cblock 0x20
 Temp
 endc

                        org 0
 ;================================================
 ; Initialize
 init:
    clrf    PORTB            ; Configure RB7 on PORTB for
    bcf     TRISB, RB7       ;  digital I/O for an LED.

    bcf     TRISC, RC6       ; Set TRISC<6:7> to enable.
              pic Pin 37 (xmt)
    bsf     TRISC, RC7       ;  serial.
              pic Pin 38 (rcv)

    bcf     PORTB, RB7       ; Turn LED off.  pic Pin 47

    movlw   0x67             ;  serial eusart to 9600 (0x19 with BRGH=0)
    movwf   SPBRG1           ;  baud.
(0x67 with BRGH=1)

     movlw   b'00100100'      ; Enable Transmit and clear SYNC
    movwf   TXSTA1           ; to allow asynchronous mode.
       movlw   b'10010000'      ; Enables Serial Port      movwf
RCSTA1                         ; and Continuous Receive
      bcf     RCSTA1, CREN           ; Clear any errors by disbaling
nop                                         ; continuous receive mode,
then     bsf     RCSTA1, CREN         ; renable conitnuous receive mode
        receive        bsf                PORTB, 7
        movf        RCREG1,W
        nop
        nop
        btfss        PIR1,5        ; (5) check for received data RC1IF
        goto        $ - 2
    movf        RCREG1,W          ; save received data in W     bcf
          PORTB, 7
    toggle:                      ; Toggle back and forth
    btg     Temp, 0          ;  between loading 'U'
    btfsc   Temp, 0          ;  and loading 'G' in the
    goto    load_U           ;  W register.
    goto    load_G           ;  ...


 load_U:          bsf                LATB,7                    ;  ...
        movlw        'R'         ;  Put 'R' in W and
        call        tx
        movlw        'B'
        call        tx
        movlw        '7'
        call        tx
        movlw        ' '
        call        tx
        movlw       'O'          ;  Put 'G' in W and
        call        tx
        movlw        'n'
        call        tx

        movlw   0x0A              ;  Put 'CR/LF' in W and transmit.
          call        tx
        movlw        0x0D
        call        tx

        btfss        PIR1,5        ; (5) wait for received data RC1IF
        goto        $ - 2
        movlw        'D'
        subwf        RCREG1,W
        btfsc        STATUS,Z
        goto    toggle
        goto        load_U
        goto    toggle


 load_G:            bcf                LATB,7                 ;  ...
        movlw        'R'              ;  Put 'G' in W and
        call        tx
        movlw        'B'
        call        tx
        movlw        '7'
        call        tx
        movlw        ' '
        call        tx
        movlw        'O'              ;  Put 'G' in W and
        call        tx
        movlw        'f'
        call        tx
        movlw        'f'
        call        tx

        movlw   0x0A              ;  Put 'CR/LF' in W and transmit.
          call        tx
        movlw        0x0D
        call        tx

        btfss        PIR1,5        ; (5) wait for received data RC1IF
        goto        $ - 2
        movlw        'U'
        subwf        RCREG1,W
        btfsc        STATUS,Z
        goto    toggle
        goto        load_G


 tx:
    movwf   TXREG            ; Move W into tx register and provide
    nop                      ;  a cycle for TXIF to update.
 check:
    btfss   PIR1, TXIF       ; Wait for tx by monitoring TXIF
    goto    check            ;  Goto check while not done.
        return
     end