Matthias,
I'm using that part pretty much like like you want to. I'm using the
DCO from a watch crystal with a 8 divider so I get an interrupt 4096
times a second. At the end of the timer/DCO interrupt I start the ADC
to take one round of readings, and when that is completed the ADC
interrupts and I flag the event using a variable I call ticks.
Once setup, there is virtually no code to keep it running and I'm
getting 4096 readings per second per channel. I found that initializing
the hardware is VERY dependent on the order of writes to device
registers - and not just the ADC.
The code is in assembly language but here it is:
ta2_isr:
push.w r15
.....code to calibrate DCO
exit_dco_ta2_isr:
pop.w r15
bis.w #START_READING,&ADC10CTL0 ;do one sequence of ADC
reti
.global init_adc ;called exactly once
init_adc:
bis.b #ADC_CHANNELS,&ADC10AE ;enable analog inputs
bis.w #ADC_CTL0,&ADC10CTL0
bis.w #ADC_CTL1,&ADC10CTL1
bis.b #ADC_DTC0,&ADC10DTC0
;
; CAVEAT below !!!!!!
; you have to write the number of transfers before giving the
; buffer address or it won't start transfers
;
mov.b #ADC_XFERS,&ADC10DTC1 ;number of transfers per block
mov.w #adc_readings,&ADC10SA ;start of buffer
ret
.global adc_isr ;one sequence is complete
adc_isr:
inc.b ticks ;ADC buffer ready to use
reti
Hope this helps.
Sincerely,
David Smead
www.amplepower.com
www.amplepower.net
On Sat, 12 Aug 2006, matthias fend wrote:
hello,
I tried to setup a MSP430F1232 to take continuous samples from a single
ADC10 channel. As trigger source I planned to use TA0.
So far so good - everything behaves as expected (continuous interrupt
occurrences).
The next step was to use the two block mode of the DTC to take some
samples triggered by TA0 and transfer them to a memory location
automatically. After the number of desired DTC transfers is done,
the ISR should evaluate the ADC samples from memory while the
ADC and the DTC are still running (using the other DTC block).
For the application it's important that the ADC samples are exactly
continuous.
But if I enable the DTC mechanism nothing happens (no interrupt
occurrences). Even if I just use a simple DTC transfer.
Attached you'll find a code snipped of a test program where I tried to
figure out these issues.
All the examples I found are using just the software trigger and
requiring a toggle of the ENC bit.
Has anybody uses the DTC in a similar way, or has anybody some ideas
what I am doing wrong ?
thanks,
matthias
#define ADC_BLOCK_SAMPLES 2
static unsigned int adc_block_mem[2*ADC_BLOCK_SAMPLES];
volatile unsigned char isig = 0;
int main(void)
{
... clock setup
/*
* timer A setup
*/
CCR0 = 60000-1; // CCR0 period
CCTL0 = OUTMOD_4; // CCR0 toggle
TACTL = TASSEL_1 | MC0; // ACLK, up
/*
* ADC10 setup
*/
ADC10CTL0 &= (~ENC | ADC10ON);
while(ADC10CTL1 & BUSY)
;
ADC10CTL0 = SREF_2 | ADC10SHT_0 | MSC | ADC10ON | ADC10IE; // 64 x
ADCCLK, multiple conversions, ADC core on, enable int
ADC10CTL1 = INCH_0 | SHS_2 | CONSEQ_2; // A0,
TA0 trigger, repeat single channel
ADC10AE = P2_GYRO_SIG_IN | P2_GYRO_REF_IN; // ADC
option select
ADC10SA = &adc_block_mem[0];
ADC10DTC0 = ADC10TB | ADC10CT; // two
block, continous transfer
#define WORKING
#ifdef WORKING
// leave ADC10DTC1 to deactivte DTC
#else
ADC10DTC1 = ADC_BLOCK_SAMPLES; //
ADC_SAMPLES conversions
#endif
_EINT(); // enable interrupts
ADC10CTL0 |= ENC;
while(1)
{
while(!isig)
;
// do something
isig = 0;
}
}
// ADC10 interrupt service routine
interrupt (ADC10_VECTOR) ADC10_ISR(void)
{
isig = 1;
}
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