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  1. #1

    Default Learning how to use USART

    I'm trying to get one PIC to talk to the other. I'm not using MIDI messages at this point, but I am using MIDI hardware to connect the two PICs. The schematics are found here https://www.tigoe.com/pcomp/code/picbasic-pro/161/

    I'm using two 16F887. One is the transmitting PIC. MIDI out hardware is connected to pin 25/portc.6/TX. I'm trying to send the numbers 1 ~ 9 every 600ms. An LED blinks each time it's supposed to send just to let me know that it's doing something.

    The other PIC is supposed to receive the number and display it on an LCD. The MIDI in hardware is connected to pin 26/portC.7/RC. I made the LCD display "ready to receive" at start up so I know that it's working.

    The blinking LED on the transmitting PIC is working, and the LCD on the receiving PIC is working, but I'm not seeing any numbers being displayed.

    Here's the code for the transmitting PIC:
    Code:
    define OSC 20
    define HSER_RCSTA 90h
    define HSER_TXSTA 20h
    define HSER_BAUD 31250
    
    
    ANSEL = %00000000
    ANSELH = %00000000
    TRISD = %00000000
    TRISE = %00000000
    TRISA = %00000000
    TRISB = %00000000
    TRISC = %01000000
    
    
    send var byte
    
    
    main:
    
    
    send = send + 1
    hserout [send]
    PORTA.0 = 1
    pause 300
    PORTA.0 = 0
    pause 300
    if send >= 10 then
        send = 0
    endif
    
    
    goto main
    Here's the code for the receiving PIC:
    Code:
    CLEARdefine LOADER_USED 1
    define OSC 20
    define HSER_RCSTA 90h
    define HSER_TXSTA 20h
    define HSER_BAUD 31250
    define LCD_DREG PORTD
    define LCD_DBIT 0
    define LCD_RSREG PORTE
    define LCD_RSBIT 0
    define LCD_EREG PORTE
    define LCD_EBIT 1
    define LCD_RWREG PORTE
    define LCD_RWBIT 2
    define LCD_BITS 4
    define LCD_LINES 4
    define LCD_COMMANDUS 2000
    define LCD_DATAUS 50
    
    
    ANSEL = %00000000
    ANSELH =%00000000
    TRISD = %00000000
    TRISE = %00000000
    TRISA = %00000000
    TRISB = %00000000
    TRISC = %01000000
    
    
    data_in var byte
    
    
    pause 250
    lcdout $fe, 1
    lcdout $fe, $d4, "ready to receive"
    pause 500
    lcdout $fe, 1
    pause 250
    
    
    main:
    
    
    hserin [dec data_in]
    pause 5
    if data_in != 0 then
    gosub display
    endif
    goto main
    
    
    display:
    lcdout $fe, 1
    lcdout $fe, $94, dec data_in
    data_in = 0
    return
    Last edited by keithv; - 9th May 2018 at 20:26.

  2. #2
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    Default Re: Learning how to use USART

    LCDs speak in ASCii. The PBP3 Reference Manual covers ASCii on pages 42 & 305-6. To work with decimal, add 48 to your decimal value & it should appear on the LCD screen as the value intended.

  3. #3

    Default Re: Learning how to use USART

    Quote Originally Posted by mpgmike View Post
    LCDs speak in ASCii. The PBP3 Reference Manual covers ASCii on pages 42 & 305-6. To work with decimal, add 48 to your decimal value & it should appear on the LCD screen as the value intended.
    That didn't help. I also realized that PORTC register should have been TRISC=%10000000. I fixed that, but it didn't help either.

  4. #4
    Join Date
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    Location
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    Default Re: Learning how to use USART

    There is an initialization process to get LCDs to come on line. It usually isn't needed, but I ran into an instance like yours where everything suggested it SHOULD work, but it didn't. One of the HD44780 LCD Data Sheets outlined an initialization process. Here is what I use:

    4-Wire
    Code:
    Init_LCD:
        RS = 0
    '    LCD = $20
        DB7 = 0
        DB6 = 0
        DB5 = 1
        DB4 = 0
            En = 1
            pauseus 10
            En = 0
            pause 5
    '    LCD = $20
        DB7 = 0
        DB6 = 0
        DB5 = 1
        DB4 = 0
            En = 1
            pauseus 10
            En = 0
            pauseus 160
    '    LCD = $20
        DB7 = 0
        DB6 = 0
        DB5 = 1
        DB4 = 0
            En = 1
            pauseus 10
            En = 0
            pauseus 160
        LCD = $28
            gosub Send
        LCD = $10
            gosub Send
        LCD = $0C
            gosub Send
        LCD = $06
            gosub Send
        LCD = 1
            gosub Send
            pause 1
        LCD = $80
            gosub Send
        RS = 1
        pause 1
    RETURN
    For 8-wire:
    Code:
    Init_LCD:
        low RS
        PORTB = $30
            high En
            pauseus 4
            low En
            pause 5
        PORTB = $30
            high En
            pauseus 4
            low En
            pauseus 160
        PORTB = $30
            high En
            pauseus 4
            low En
            pauseus 160
        PORTB = $38
            gosub Send
        PORTB = $10
            gosub Send
        PORTB = $0C
            gosub Send
        PORTB = $06
            gosub Send
        PORTB = 1
            gosub Send
            pause 1
        PORTB = $80
            gosub Send
        high RS
        pause 1 
    RETURN
    
    Send:
        high En
        pauseus 8
        low En
        pause 1
    return
    Maybe this will help.

  5. #5
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    Default Re: Learning how to use USART

    The blinking LED on the transmitting PIC is working, and the LCD on the receiving PIC is working, but I'm not seeing any numbers being displayed.
    given all things working display wise ,imho mike is leading you astray

    tx unit:-

    send = send + 1
    hserout [send]

    will send binary 0 to 9 , probably not the best idea but it is workable


    ps weird baud rate


    rx unit:-


    hserin [dec data_in]
    pause 5


    will never work

    1. its waiting for ascii numbers , the first non number will terminate routine
    2. pause 5 why it serves no purpose and can cause framing errors


    add this define
    DEFINE HSER_CLROERR 1 ' Clear overrun error upon execution of every HSERIN command


    rx unit:-
    lcdout $fe, $94, dec data_in

    if ok but it needs
    hserin [data_in] to match data types

    ps weird baud rate
    Last edited by richard; - 10th May 2018 at 05:09.
    This is more entertaining than Free to Air TV

  6. #6

    Default Re: Learning how to use USART

    Yes, the LDC is working just fine. The baud rate is the standard MIDI baud rate. I'm trying to make a MIDI controller.

    I've updated the code with the suggestions and made it a little more simple. I'm trying to get the LCD of the receiving PIC to display "1" for 300ms and then "0" for 300ms.

    Here's the code for the transmitting PIC:
    Code:
    define OSC 20
    define HSER_RCSTA 90h
    define HSER_TXSTA 20h
    define HSER_BAUD 31250
    
    
    ANSEL = %00000000
    ANSELH = %00000000
    TRISD = %00000000
    TRISE = %00000000
    TRISA = %00000000
    TRISB = %00000000
    TRISC = %10000000
    
    main:
    
    hserout [1]
    PORTA.0 = 1
    pause 300
    hserout [0]
    PORTA.0 = 0
    pause 300
    
    goto main
    Here's the code for the receiving PIC:
    Code:
    CLEAR
    define LOADER_USED 1
    define OSC 20
    define HSER_RCSTA 90h
    define HSER_TXSTA 20h
    define HSER_BAUD 31250
    define HSER_CLROERR 1
    define LCD_DREG PORTD
    define LCD_DBIT 0
    define LCD_RSREG PORTE
    define LCD_RSBIT 0
    define LCD_EREG PORTE
    define LCD_EBIT 1
    define LCD_RWREG PORTE
    define LCD_RWBIT 2
    define LCD_BITS 4
    define LCD_LINES 4
    define LCD_COMMANDUS 2000
    define LCD_DATAUS 50
    
    ANSEL = %00000000
    ANSELH = %00000000
    TRISD = %00000000
    TRISE = %00000000
    TRISA = %00000000
    TRISB = %00000000
    TRISC = %10000000
    
    character var byte
    
    pause 250
    lcdout $FE, 1
    lcdout $fe, $d4, "ready to receive"
    pause 500
    lcdout $fe, 1
    pause 250
    
    main:
    
    hserin [character]
    lcdout $fe, 1
    lcdout $fe, $94, character
    
    goto main
    It's still not working.

  7. #7
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    Default Re: Learning how to use USART

    It's still not working.
    how can it work ?
    char's 0 and 1 are non printing characters on a lcd

    lcdout $fe, $94, dec character
    This is more entertaining than Free to Air TV

  8. #8

    Default Re: Learning how to use USART

    Quote Originally Posted by richard View Post
    how can it work ?
    char's 0 and 1 are non printing characters on a lcd

    lcdout $fe, $94, dec character
    Adding the dec modifier didn't help. I tried adding it to hserout as well and it didn't work. Maybe it's my hardware. This is what I'm trying to use.

    Name:  midi-schem.jpg
Views: 73
Size:  21.4 KB

    Can you recommend something else that's better for connecting two PICs?

  9. #9
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    Default Re: Learning how to use USART

    Can you recommend something else that's better for connecting two PICs?
    it can't get simpler than this depending on distance / speed .
    using serial tty ie hserin/out
    Attached Images Attached Images  
    This is more entertaining than Free to Air TV

  10. #10
    Join Date
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    Posts
    566

    Default Re: Learning how to use USART

    I would get the two talking directly without any MIDI interface. Just connect the TX from the PIC running the transmission code, to the RX on the receiving PIC using a simple jumper wire. If you need to send data back the connect the receiving PICs TX pin to the RX pin on the other PIC. I would then use the HSEROUT and HSERIN commands to send data.

    You could write a short test routine so that the receiving PIC sends a character to the transmitting PIC when its ready to receive data (say by pressing a button), the transmission is made and the data displayed on the LCD.

    So your transmission PIC has something like
    Code:
    RCIF              VAR PIR1.5                    ' USART receive flag
    GIE               VAR INTCON.7                  ' Comms
    TempWD            VAR WORD                      ' temporary WORD variable
    nTest var byte
    
    
    FOR TempWD = 0 TO 1000
        IF RCIF=1 THEN GOTO coms                   ; Check to see if somethings in the buffer, if there is something goto Comms   
        PAUSE 2
    NEXT TempWD  
    
    coms:
    HSERIN [nTest]
        SELECT CASE nTest    
        CASE "Q"                    ; if Q then send data 
        GOTO Term_TX:
    
    Term_TX
    Hserout [DEC3 insert variable here] ; sends three digits of variable eg 123
    You would then have your receiving PIC set up so that when you want to receive data it sends a Q to the transmitting PIC. The transmitting PIC is always looking at the serial port buffer to see if there is something in it, and when it finds something jumps to the comms subroutine, which checks to see what character has been received an for a match. If its Q then it transmits the data. You could use other characters to jump to other routines and do other things if you wanted.

    The only caveat here is that I've only ever sent numeric data this way. Sending ASCII or strings may need more work.

    Whilst the code is clunky it could always be tidied up and made more efficient once you have the two talking.

  11. #11
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    Default Re: Learning how to use USART

    Strange baudrate !

    Using a EUSART calculator for your baudrate it gives these values for the port settings

    Code:
    DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
    DEFINE HSER_TXSTA 20h ' Enable transmit, BRGH = 0
    DEFINE HSER_CLROERR 1 ' Clear overflow automatically
    DEFINE HSER_SPBRG 39  ' 31250 Baud @ SPBRGH = 0
    BAUDCON.3 = 1         ' Enable 16 bit baudrate generator
    
    
    RCSTA = $90   ' Enable serial port & continuous receive
    TXSTA = $20   ' Enable transmit, BRGH = 0
    SPBRG = 39    ' 31250 Baud @ 0.0%
    SPBRGH = 0
    BAUDCON.3 = 1 ' Enable 16 bit baudrate generator
    I don't have PBP3 - so no idea if the formatting is the same or needs changing

  12. #12
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    Default Re: Learning how to use USART

    Please make sure that PIC to PIC directly connected work as expected.

    Then move to MIDI interface.

    Also be sure to connect TX to RX. Looks trivial but...

    Ioannis

  13. #13

    Default Re: Learning how to use USART

    I removed the midi connections and just connected the TX of the transmitting PIC to the RC of the receiving PIC. Here is the code I'm using for each:

    transmitting:
    Code:
    define OSC 20
    define HSER_RCSTA 90h
    define HSER_TXSTA 20h
    define HSER_BAUD 31250
    DEFINE HSER_SPBRG 39  ' 31250 Baud @ SPBRGH = 0
    
    
    
    ANSEL = %00000000
    ANSELH = %00000000
    TRISD = %00000000
    TRISE = %00000000
    TRISA = %00000000
    TRISB = %00000000
    TRISC = %10000000
    
    main:
    
    hserout [dec 1]
    PORTA.0 = 1
    pause 300
    hserout [dec 0]
    PORTA.0 = 0
    pause 300
    
    goto main
    receiving:
    Code:
    CLEAR
    define LOADER_USED 1
    define OSC 20
    define HSER_RCSTA 90h
    define HSER_TXSTA 20h
    define HSER_BAUD 31250
    define HSER_CLROERR 1
    DEFINE HSER_SPBRG 39  ' 31250 Baud @ SPBRGH = 0
    
    define LCD_DREG PORTD
    define LCD_DBIT 0
    define LCD_RSREG PORTE
    define LCD_RSBIT 0
    define LCD_EREG PORTE
    define LCD_EBIT 1
    define LCD_RWREG PORTE
    define LCD_RWBIT 2
    define LCD_BITS 4
    define LCD_LINES 4
    define LCD_COMMANDUS 2000
    define LCD_DATAUS 50
    
    ANSEL = %00000000
    ANSELH = %00000000
    TRISD = %00000000
    TRISE = %00000000
    TRISA = %00000000
    TRISB = %00000000
    TRISC = %10000000
    
    character var byte
    
    pause 250
    lcdout $FE, 1
    lcdout $fe, $d4, "ready to receive"
    pause 500
    lcdout $fe, 1
    pause 250
    
    main:
    
    hserin [character]
    lcdout $fe, 1
    lcdout $fe, $94, dec character
    
    goto main
    So now it's sorta working. The LCD does display something. It displays "216" when it should be displaying "0" and it displays "217" when it should be displaying 1.

  14. #14
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    Posts
    566

    Default Re: Learning how to use USART

    Try setting a variable.
    Code:
    character  var word
    then use something like

    Code:
    hserout [dec character]
    And similar for the receiving pic. I'm no expert, but I think that just having DEC 1 as you had simply means its setting the DEC command to use just 1 digit as decimal value of a variable, not a value
    Last edited by Scampy; - 14th May 2018 at 20:44.

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