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Last Modified: 21 November 2000 |
6172 CAN Micro Controller Module AN003
This application example is not yet completely tested
24 bit analog input with AD7712
This application example enables the user to use a -10...10Volt analog input with a resolution of 1.2µV.
The AD7712 is configured to use its 10V input, it is default set to a sample rate of 10 Hz (recommended for highest precision).
By tying the DRDY output of the 7712 to (level sensitive) IN8 of the 6172, this application will automatically transmit a PDO every 100 mS (if the analog input value has changed).
header "AD7712 A/D converter AN003"
advalue:equ 0 ;A/D value memory location
config: equ 4 ;A/D converter configuration value
a0bit: equ 1 ;A0 (AD7712) input bit number (OUT10)
tfsbit: equ 2 ;TFS (AD7712) input bit number (OUT11)
rfsbit: equ 3 ;RFS (AD7712) input bit number (OUT12)
rdybit: equ 7 ;DRDY (AD7712) output bit number (IN8)
;default configuration (a 24 bit number) will select:
;bit
;23-21: operating mode = %001: active self calibration, normal mode when
; finished (after 9 sample cycles)
;20-18: gain = %000: gain = 1 (full scale = 10V)
; 17: channel = 1: select AIN2 input
; 16: power down = 0: normal operation
; 15: word length = 1: output word is 24 bits
; 14: unused
; 13: burnout current = 0: no burnout current (AIN1 input)
; 12: bipolar/unipolar = 0: -10...10V input
;11- 0: filter selection = $7A1: filter/sample rate = 10Hz
configh:equ %00100010
configm:equ %1000 shl 4 + $7
configl:equ $A1
;initialization sequence
sequence seq_0
setb tfsbit ;TFS inactive state
setb rfsbit ;RFS inactive state
shspd 1 ;SPI shifter at 1.1 µS/bit
shpat 0 ;normal data, no shifted clock
srdy ;READY output active
ldwc configh ;set default config value in
stwm config + 1 ;lower 3 bytes of the config location
ldwc configm
stwm config + 2
ldwc configl
stwm config + 3
call seq_3 ;write config to AD7712, start self-calibration
seqcl seq_4,0,rdybit ;activate sequence 2 on low level of IN8
enasq 0 ;enable sequences
endsq
;write config to AD7712
sequence seq_3,,config+3 ;start on write of config+3
resb a0bit ;A0 low to access control register
resb tfsbit ;TFS active
shom config+1 ;write current config to AD7712
shom config+2
shom config+3
setb tfsbit ;TFS inactive, calibration now starts
endsq
;read sample from AD7712, this sequence is started when IN8 (DRDY) is low
sequence seq_4
setb a0bit ;A0 high to access data register
resb rfsbit ;RFS active
shim advalue ;read 24 bit result into advalue
shim advalue+1
shim advalue+2
setb rfsbit ;RFS inactive, DRDY (IN8) will go high
endsq
end
Assuming that all 6172 objects are in their default state, the following objects need to be adjusted.
|
Index |
Subindex |
Value |
Description |
|---|---|---|---|
|
Receive PDO 1 is set for a 32 bits unsigned integer with the AD7712 configuration in the lower 24 bits |
|||
|
1600h |
0 |
1 |
1 object in receive PDO 1 |
|
1600h |
1 |
63200220h |
memory location 4 - 7 |
|
Transmit PDO 1 should be treated as a signed 32 bits integer with the A/D value in the higher 24 bits |
|||
|
1A00h |
0 |
1 |
1 object in transmit PDO 1 |
|
1A00h |
1 |
61200120h |
memory location 0 - 3 |
|
Enable interrupt on change of memory locations 0 - 2 |
|||
|
6006h |
1 |
255 |
enable interrupt on any change of location 0 |
|
6006h |
2 |
255 |
enable interrupt on any change of location 1 |
|
6006h |
3 |
255 |
enable interrupt on any change of location 2 |
The AD7712 configuration can be changed by:
The AD7712 sample can be read by:
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 one 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"
'The 6172 will be enabled to send its PDO on any change, the PDO will be
'requested if no PDO was received within 5 seconds.
'pressing ENTER exits the program
CLS
PRINT "CD Systems 6172 AN003 DEMO program"
PRINT
Activate6390 2, 19200 '6390 works at COM2, 19200 BAUD
SetCANBUSSpeed 50 'CAN BUS at 50 kBAUD
C% = CheckSequence%(1, "AN003.seq") 'download sequence if not already done
C% = PutU8% (1, &h1600, 0, 1) '1 object in receive PDO1
C% = PutU32% (1, &h1600, 1, &h63200220) 'receive PDO1 to memory 4..7
C% = PutU8% (1, &h1A00, 0, 1) '1 object in transmit PDO1
C% = PutU32% (1, &h1A00, 1, &h61200120) 'transmit PDO1 from memory 0..3
C% = PutU8% (1, &h6006, 1, 255) 'enable transmit PDO on any change
C% = PutU8% (1, &h6006, 2, 255)
C% = PutU8% (1, &h6006, 3, 255)
SendNMTCommand (1, 1) 'node in operational state
BT = TIMER
PDOCOB% = (1 + 384) * 32 'tx PDO1 COB ID shifted left 5 bits
DO
' send a transmit PDO1 remote request if nothing received after 5 seconds
IF (BT + 5) < TIMER THEN
SendToCAN (CANIDS$ (PDOCOB% + &h10))
BT = TIMER
END IF
' check if the transmit PDO is received
R$ = ReceiveFromCAN$
IF LEN (R$) > 1 THEN 'anything received?
IF (CANIDR% (R$) AND &hFFE0) = PDOCOB% THEN 'PDO1 tx received?
AD& = CVL (MID$(R$, 3, 4)) 'get signed AD value
AD& = AD& / 256 'shift right 8 bits
V# = AD& / 2^23 * 10 'convert to voltage
PRINT USING "D/A value: ######## = ##.######Volt"; AD&, V#
BT = TIMER
END IF
END IF
LOOP UNTIL INKEY$ = CHR$(13)
SendNMTCommand (1, 2) 'stop node
DO 'clear & ignore any received message
R$ = ReceiveFromCAN$
LOOP UNTIL R$ = ""
END