Sojus07/hackrf
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

max2837: divisor registers calculated using long division

Browse Source
This commit is contained in:
Will Code
2012-05-30 21:01:34 -04:00
parent 2e905170f8
commit 9de62e27c8
1 changed files with 20 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
firmware/common/max2837.c
View File

@ -136,7 +136,10 @@ void max2837_set_frequency(uint32_t freq)
{ {
uint8_t band; uint8_t band;
uint32_t div_frac; uint32_t div_frac;
uint8_t div_int; uint32_t div_int;
uint32_t div_rem;
uint32_t div_cmp;
int i;
/* Select band. Allow tuning outside specified bands. */ /* Select band. Allow tuning outside specified bands. */
if (freq < 2400000000) if (freq < 2400000000)
@ -150,9 +153,22 @@ void max2837_set_frequency(uint32_t freq)
LOG("# max2837_set_frequency %ld, band %d\n", freq, band); LOG("# max2837_set_frequency %ld, band %d\n", freq, band);
/* TODO - frac vs int, compute values */ /* ASSUME 40MHz PLL. Ratio = F*(4/3)/40,000,000 = F/30,000,000 */
div_int = 0x12; div_int = freq / 30000000;
div_frac = 0x34567; div_rem = freq % 30000000;
div_frac = 0;
div_cmp = 30000000;
for( i = 0; i < 20; i++) {
div_frac <<= 1;
div_cmp >>= 1;
if (div_rem > div_cmp) {
div_frac |= 0x1;
div_rem -= div_cmp;
}
}
LOG("# int %ld, frac %ld\n", div_int, div_frac);
//
/* Write order matters here, so commit INT and FRAC_HI before /* Write order matters here, so commit INT and FRAC_HI before
* committing FRAC_LOG, which is the trigger for VCO * committing FRAC_LOG, which is the trigger for VCO