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Merge pull request #606 from atiselsts/master

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Fix MCU clock calibration in msp430f2xxx based platforms (e.g. Zolertia Z1)
This commit is contained in:
Nicolas Tsiftes 2014-04-09 21:52:08 +02:00
commit 1b49b68c3b
1 changed files with 32 additions and 95 deletions
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127
cpu/msp430/f2xxx/msp430.c
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@ -83,68 +83,6 @@ msp430_init_dco(void)
/* DCO Internal Resistor */
}
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
/* Start CPU with full speed (? good or bad?) and go downwards */
/*---------------------------------------------------------------------------*/
void
msp430_quick_synch_dco(void) {
uint16_t last;
uint16_t diff;
uint16_t dco_reg = 0x0fff;
uint8_t current_bit = 12;
uint16_t i;
/* DELTA_2 assumes an ACLK of 32768 Hz */
#define DELTA_2 ((MSP430_CPU_SPEED) / 32768)
/* Select SMCLK clock, and capture on ACLK for TBCCR6 */
TBCTL = TBSSEL1 | TBCLR;
TBCCTL6 = CCIS0 + CM0 + CAP;
/* start the timer */
TBCTL |= MC1;
BCSCTL1 = 0x8D | 7;
DCOCTL = 0xff; /* MAX SPEED ?? */
/* IDEA: do binary search - check MSB first, etc... */
/* 1 set current bit to zero - if to slow, put back to 1 */
while(current_bit--) {
/* first set the current bit to zero and check - we know that it is
set from start so ^ works (first bit = bit 11) */
dco_reg = dco_reg ^ (1 << current_bit); /* clear bit 11..10..9.. */
/* set dco registers */
DCOCTL = dco_reg & 0xff;
BCSCTL1 = (BCSCTL1 & 0xf8) | (dco_reg >> 8);
/* some delay to make clock stable - could possibly be made using
captures too ... */
for(i=0; i < 1000; i++) {
i = i | 1;
}
/* do capture... */
while(!(TBCCTL6 & CCIFG));
last = TBCCR6;
TBCCTL6 &= ~CCIFG;
/* wait for next Capture - and calculate difference */
while(!(TBCCTL6 & CCIFG));
diff = TBCCR6 - last;
/* /\* store what was run during the specific test *\/ */
/* dcos[current_bit] = dco_reg; */
/* vals[current_bit] = diff; */
/* should we keep the bit cleared or not ? */
if(diff < DELTA_2) { /* DCO is too slow - fewer ticks than desired */
/* toggle bit again to get it back to one */
dco_reg = dco_reg ^ (1 << current_bit);
}
}
}
/*---------------------------------------------------------------------------*/
static void
init_ports(void)
{
@ -224,7 +162,10 @@ msp430_cpu_init(void)
dint();
watchdog_init();
init_ports();
msp430_quick_synch_dco();
/* set DCO to a reasonable default value (8MHz) */
msp430_init_dco();
/* calibrate the DCO step-by-step */
msp430_sync_dco();
eint();
#if defined(__MSP430__) && defined(__GNUC__)
if((uintptr_t)cur_break & 1) { /* Workaround for msp430-ld bug! */
@ -282,13 +223,10 @@ int __low_level_init(void)
}
#endif
/*---------------------------------------------------------------------------*/
#if DCOSYNCH_CONF_ENABLED
/* this code will always start the TimerB if not already started */
void
msp430_sync_dco(void) {
uint16_t last;
uint16_t diff;
/* uint32_t speed; */
uint16_t oldcapture;
int16_t diff;
/* DELTA_2 assumes an ACLK of 32768 Hz */
#define DELTA_2 ((MSP430_CPU_SPEED) / 32768)
@ -298,36 +236,35 @@ msp430_sync_dco(void) {
/* start the timer */
TBCTL |= MC1;
/* wait for next Capture */
TBCCTL6 &= ~CCIFG;
while(!(TBCCTL6 & CCIFG));
last = TBCCR6;
while(1) {
/* wait for the next capture */
TBCCTL6 &= ~CCIFG;
while(!(TBCCTL6 & CCIFG));
oldcapture = TBCCR6;
TBCCTL6 &= ~CCIFG;
/* wait for next Capture - and calculate difference */
while(!(TBCCTL6 & CCIFG));
diff = TBCCR6 - last;
/* wait for the next capture - and calculate difference */
TBCCTL6 &= ~CCIFG;
while(!(TBCCTL6 & CCIFG));
diff = TBCCR6 - oldcapture;
/* Stop timer - conserves energy according to user guide */
TBCTL = 0;
/* speed = diff; */
/* speed = speed * 32768; */
/* printf("Last TAR diff:%d target: %ld ", diff, DELTA_2); */
/* printf("CPU Speed: %lu DCOCTL: %d\n", speed, DCOCTL); */
/* resynchronize the DCO speed if not at target */
if(DELTA_2 < diff) { /* DCO is too fast, slow it down */
DCOCTL--;
if(DCOCTL == 0xFF) { /* Did DCO role under? */
BCSCTL1--;
}
} else if(DELTA_2 > diff) {
DCOCTL++;
if(DCOCTL == 0x00) { /* Did DCO role over? */
BCSCTL1++;
/* resynchronize the DCO speed if not at target */
if(DELTA_2 == diff) {
break; /* if equal, leave "while(1)" */
} else if(DELTA_2 < diff) { /* DCO is too fast, slow it down */
DCOCTL--;
if(DCOCTL == 0xFF) { /* Did DCO roll under? */
BCSCTL1--;
}
} else { /* -> Select next lower RSEL */
DCOCTL++;
if(DCOCTL == 0x00) { /* Did DCO roll over? */
BCSCTL1++;
}
/* -> Select next higher RSEL */
}
}
/* Stop the timer - conserves energy according to user guide */
TBCTL = 0;
}
#endif /* DCOSYNCH_CONF_ENABLED */
/*---------------------------------------------------------------------------*/