diff options
Diffstat (limited to 'libmaple/adc.c')
| -rw-r--r-- | libmaple/adc.c | 32 |
1 files changed, 26 insertions, 6 deletions
diff --git a/libmaple/adc.c b/libmaple/adc.c index b70c8bd..3e6818c 100644 --- a/libmaple/adc.c +++ b/libmaple/adc.c @@ -60,7 +60,9 @@ * * At 55.5 cycles/sample, the external input impedance < 50kOhms*/ -void adc_init(void) { +void set_adc_smprx(adc_smp_rate smp_rate); + +void adc_init(adc_smp_rate smp_rate) { rcc_set_prescaler(RCC_PRESCALER_ADC, RCC_ADCPRE_PCLK_DIV_6); rcc_clk_enable(RCC_ADC1); rcc_reset_dev(RCC_ADC1); @@ -70,11 +72,9 @@ void adc_init(void) { ADC_CR2 = CR2_EXTSEL_SWSTART | CR2_EXTTRIG; ADC_SQR1 = 0; - /* Up the sample conversion time to 55.5 cycles/sec, see note - above */ - /* TODO: fix magic numbers */ - ADC_SMPR1 = 0xB6DB6D; - ADC_SMPR2 = 0x2DB6DB6D; + /* Set the sample conversion time. See note above for impedance + requirements. */ + adc_set_sample_rate(smp_rate); /* Enable the ADC */ CR2_ADON_BIT = 1; @@ -93,3 +93,23 @@ void adc_init(void) { void adc_disable(void) { CR2_ADON_BIT = 0; } + +/* Turn the given sample rate into values for ADC_SMPRx. (Don't + * precompute in order to avoid wasting space). + * + * Don't call this during conversion! + */ +void adc_set_sample_rate(adc_smp_rate smp_rate) { + uint32 adc_smpr1_val = 0, adc_smpr2_val = 0; + int i; + for (i = 0; i < 10; i++) { + if (i < 8) { + /* ADC_SMPR1 determines sample time for channels [10,17] */ + adc_smpr1_val |= smp_rate << (i * 3); + } + /* ADC_SMPR2 determines sample time for channels [0,9] */ + adc_smpr2_val |= smp_rate << (i * 3); + } + ADC_SMPR1 = adc_smpr1_val; + ADC_SMPR2 = adc_smpr2_val; +} |