6172 CAN Micro Controller Module AN002

This application example is not yet completely tested

14 bit analog output with AD7840

This application example enables the user to set a -3 ... 3 Volt analog output with a resolution of 0.37 mV.

The AD7840 is configured to use the 14 most significant bits of the 16 bits it receives.
This example can be used to implement other (16 bit) D/A converters.

        header  "6172-AN002, 7840 D/A converter"
 
davalue:equ     2               ;D/A value memory location 
lsbit:  equ     0               ;OUT1 bit number in port A 
 
;-------------------------------------------------------------------
initialisation sequence 
 
        sequence seq_0 
 
        seta    lsbit           ;ldac/sync high 
        shspd   1               ;SPI shifter at 1.1 µS/bit 
        shpat   1               ;normal data, phase shifted clock 
        srdy                    ;READY output active 
 
;write zero to the D/A converter (sets output at 0 Volt) 
 
        ldwm    0               ;clear working register 
        resa    lsbit           ;ldac/sync low 
        stwm    spiout          ;high byte 
        stwm    spiout          ;low byte 
        seta    lsbit           ;ldac/sync high 
        enasq   3               ;enable sequence 3
        endsq 
;-------------------------------------------------------------------
;update D/A converter sequence, after a write to address DAVALUE + 1 
 
        sequence seq_3,,davalue+1 
        resa    lsbit           ;ldac/sync low 
        shom    davalue         ;msb to D/A converter 
        shom    davalue+1       ;lsb to D/A converter 
        seta    lsbit           ;ldac/sync high 
        endsq                   ;done 
;-------------------------------------------------------------------
        end

Assuming that all 6172 objects are in their default state, the following objects need to be adjusted (if a PDO is used):

 

Index	Subindex	Value	Description
1600h	0	2	2 objects in receive PDO 1
1600h	1	62000208h	memory location 2
1600h	2	62000308h	memory location 3

The DAVALUE can now be set by:

• sending PDO 1 to the 6172
  (60 bits message)
• writing object 6320h, subindex 1, using one SDO write with data in lower 16 bits of 32 bits number
  (2 x 108 bits messages)
• writing object 6200h, subindex 3 and 4, using two SDO writes
  (4 x 108 bits messages)

Copy and Paste this part direct after the declarations in the canappl.bas program
this program can be found on the 6197 designers kit diskette or
ordered separately as service part together with our of our CAN products  

APPLICATION:
 
'This simple program is made for one 6172 and a 6390 as CAN bus interface
'the following assumptions are done:
'- 6390 is connected to COM2
'- 6172 ID = 1, CANbus speed = 50 kBAUD
'- assembled sequence file is "AN002.seq"
 
'As long as the user enters a number, the programs sends this to the 6172
'using a 32 bit SDO write
'entering nothing (just pressing ENTER) exits the program
 
CLS
PRINT "CD Systems 6172 AN002 DEMO program"
PRINT
 
Activate6390 2, 19200                          '6390 works at COM2, 19200 BAUD
SetCANBUSSpeed 50                                         'CAN BUS at 50 kBAUD
 
C% = CheckSequence%(1, "AN002.seq")     'download sequence if not already done
 
'because the D/A value is set with a SDO command, the node doesn't have
'to be put in operational state (NMT command)
 
DO
  INPUT "Enter a integer value (-31768 ... 31767)"; DAVAL$
  IF DAVAL$ <> "" THEN
     DAVAL& = VAL(DAVAL$)
     PRINT
     PRINT "Transfer ";
     IF PutSDOObject(1, &H6320, 1, MKL$(DAVAL&)) = 0 THEN PRINT "un";
     PRINT "succesfull"
     PRINT
  END IF
LOOP UNTIL DAVAL$ = ""
 
END