Learning how to use USART

[keithv]

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.



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

[richard]

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

[Scampy]

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

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.

[Scampy]

Strange baudrate !

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

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

[Ioannis]

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

[keithv]

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:

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:

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.

[Scampy]

Try setting a variable.

character  var word

then use something like

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