4-20mA using SPI Interface

Hi All,

I came across a 4-20mA board from MicroElektronika which uses the SPI to control the device, has anyone used such a board before?, I am looking for Code Examples, would anyone be able to assist?

Regards,

gavo

Is it too much to ask to at least post a link to the board in question?
I could try to find it on their site but I won't so the best answer *I* can give you is that you can use SHIFTOUT to do bitbanged SPI or use the MSSP module (if the PIC has one) to do it "in hardware".

/Henrik.

Hi

This is some code I wrote to use that board as a basic loop calibrator. Worked OK for me.

Take care

Alec

Code:

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'****************************************************************
'*  Name    : Encoder test                                      *
'*  Author  : alec noble                                        *
'*  Notice  : Copyright (c) 2012 alec noble                    *
'*          : All Rights Reserved                              *
'*  Date    : 9/27/2012                                        *
'*  Version : 1.0                                              *
'*  Notes  :                                                  *
'*          :                                                  *
'****************************************************************
#CONFIG
    __config _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_ON & _LVP_OFF & _CP_OFF
#ENDCONFIG

'DEFINE OSC 20

'************************** setup LCD ****************************

        DEFINE        LCD_DREG        PORTB                ' Set Data to PortB
        DEFINE        LCD_DBIT        0                        ' Set starting Data to Bit4
        DEFINE        LCD_RSREG  PORTB                ' Set Register Select to PortB
        DEFINE        LCD_RSBIT  4                        ' Set RS line to PORTB.4
        DEFINE        LCD_EREG        PORTB                ' Set Enable to PortB
        DEFINE        LCD_EBIT          5                        ' Set Enable line to PortB.5
        DEFINE        LCD_BITS        4                        ' Set for 4 bit Bus
        DEFINE        LCD_LINES        2                        ' Set number of lines to

'*********************************************************************
CMCON = 7          'comparaters off - digital I/O on port A

trisb = 0          'all bits outputs
trisa = %00000111  'porta.0, 1, 2 input, all others output




cntr    var word
cntr_1  var word
cntr_2  var word
preset  var byte

sck var porta.6
sdi var porta.7
cs  var porta.4


cntr = 200
preset = 0
cs = 1

lcdout $FE, $01
pause 5
lcdout  "ahn_loop_cal"

pause 5000

lcdout $FE, $01
pause 5
lcdout dec cntr

'************************  Program **********************************

main:
    if porta.2 = 1 then set
    if porta.0 = 1 then CW
    if porta.1 = 1 then CCW
    goto main
   
    set:
    pause 5
    if porta.2 = 0 then main
    preset = preset + 1
    while porta.2 = 1 : wend
    if preset  > 4 then preset = 0
    lookup2 preset, [200, 400, 600, 800, 1000], cntr
    goto display
   
    CW:
    pause 5
    if porta.0 = 0 then main
    if cntr = 1023 then main
    cntr = cntr + 1
    goto display
   
   
    CCW:
    pause 5
    if porta.1 = 0 then main
    if cntr < 190 then main
    cntr = cntr - 1
    goto display
   
    display:
    cntr_1 = cntr * 4
    lcdout $FE, $01, dec cntr_1, " mV"
    pause 5
    cntr_2 = cntr_1/2
    lcdout $FE, $C0, dec2 cntr_2/100, ".", dec2 cntr_2//100, " mA"
    goto DAC_out
   
DAC_out:

   
    cntr_1.15 = 0
    cntr_1.14 = 0
    cntr_1.13 = 1      'GAIN OF 1
    cntr_1.12 = 1      'turn on DAC output
    low CS
'    pause 5
    shiftout sdi, sck, 1, [cntr_1\16]
    high cs
       
    while porta.0 or porta.1 = 1
    wend
   
    goto main

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Hi Alec,

Many Thanks!, will try it!,

Hendrik the link is http://www.mikroe.com/click/rs485-5v/

Regards,

Gavin