diff options
Diffstat (limited to 'fw/adc.c')
| -rw-r--r-- | fw/adc.c | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/fw/adc.c b/fw/adc.c new file mode 100644 index 0000000..726e9a8 --- /dev/null +++ b/fw/adc.c @@ -0,0 +1,118 @@ +/* Megumin LED display firmware + * Copyright (C) 2018 Sebastian Götte <code@jaseg.net> + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + */ + +#include "adc.h" + +volatile struct adc_measurements adc_data = {0}; + +enum adc_channels { + VREF_CH, + VMEAS_A, + VMEAS_B, + TEMP_CH, + NCH +}; +static volatile uint16_t adc_buf[NCH]; + +void adc_init(void) { + /* The ADC is used for temperature measurement. To compute the temperature from an ADC reading of the internal + * temperature sensor, the supply voltage must also be measured. Thus we are using two channels. + * + * The ADC is triggered by compare channel 4 of timer 1. The trigger is set to falling edge to trigger on compare + * match, not overflow. + */ + ADC1->CFGR1 = ADC_CFGR1_DMAEN | ADC_CFGR1_DMACFG | (2<<ADC_CFGR1_EXTEN_Pos) | (1<<ADC_CFGR1_EXTSEL_Pos); + /* Clock from PCLK/4 instead of the internal exclusive high-speed RC oscillator. */ + ADC1->CFGR2 = (2<<ADC_CFGR2_CKMODE_Pos); /* Use PCLK/4=12MHz */ + /* Sampling time 13.5 ADC clock cycles -> total conversion time 2.17us*/ + ADC1->SMPR = (2<<ADC_SMPR_SMP_Pos); + /* Internal VCC and temperature sensor channels */ + ADC1->CHSELR = ADC_CHSELR_CHSEL0 | ADC_CHSELR_CHSEL1 | ADC_CHSELR_CHSEL16 | ADC_CHSELR_CHSEL17; + /* Enable internal voltage reference and temperature sensor */ + ADC->CCR = ADC_CCR_TSEN | ADC_CCR_VREFEN; + /* Perform ADC calibration */ + ADC1->CR |= ADC_CR_ADCAL; + while (ADC1->CR & ADC_CR_ADCAL) + ; + /* Enable ADC */ + ADC1->CR |= ADC_CR_ADEN; + ADC1->CR |= ADC_CR_ADSTART; + + /* Configure DMA 1 Channel 1 to get rid of all the data */ + DMA1_Channel1->CPAR = (unsigned int)&ADC1->DR; + DMA1_Channel1->CMAR = (unsigned int)&adc_buf; + DMA1_Channel1->CNDTR = NCH; + DMA1_Channel1->CCR = (0<<DMA_CCR_PL_Pos); + DMA1_Channel1->CCR |= + DMA_CCR_CIRC /* circular mode so we can leave it running indefinitely */ + | (1<<DMA_CCR_MSIZE_Pos) /* 16 bit */ + | (1<<DMA_CCR_PSIZE_Pos) /* 16 bit */ + | DMA_CCR_MINC + | DMA_CCR_TCIE; /* Enable transfer complete interrupt. */ + DMA1_Channel1->CCR |= DMA_CCR_EN; /* Enable channel */ + + /* triggered on transfer completion. We use this to process the ADC data */ + NVIC_EnableIRQ(DMA1_Channel1_IRQn); + NVIC_SetPriority(DMA1_Channel1_IRQn, 3<<5); +} + +uint16_t buf_a[256]; +uint16_t buf_b[256]; +int bufp = 0; + +void DMA1_Channel1_IRQHandler(void) { + /* This interrupt takes either 1.2us or 13us. It can be pre-empted by the more timing-critical UART and LED timer + * interrupts. */ + static int count = 0; /* oversampling accumulator sample count */ + static uint32_t adc_aggregate[NCH] = {0}; /* oversampling accumulator */ + + /* Clear the interrupt flag */ + DMA1->IFCR |= DMA_IFCR_CGIF1; + + for (int i=0; i<NCH; i++) + adc_aggregate[i] += adc_buf[i]; + + if (++count == (1<<ADC_OVERSAMPLING)) { + for (int i=0; i<NCH; i++) + adc_aggregate[i] >>= ADC_OVERSAMPLING; + /* This has been copied from the code examples to section 12.9 ADC>"Temperature sensor and internal reference + * voltage" in the reference manual with the extension that we actually measure the supply voltage instead of + * hardcoding it. This is not strictly necessary since we're running off a bored little LDO but it's free and + * the current supply voltage is a nice health value. + */ + adc_data.adc_vcc_mv = (3300 * VREFINT_CAL)/(adc_aggregate[VREF_CH]); + + int64_t read = adc_aggregate[TEMP_CH] * 10 * 10000; + int64_t vcc = adc_data.adc_vcc_mv; + int64_t cal = TS_CAL1 * 10 * 10000; + adc_data.adc_temp_celsius_tenths = 300 + ((read/4096 * vcc) - (cal/4096 * 3300))/43000; + + adc_data.adc_vmeas_a_mv = (adc_aggregate[VMEAS_A]*13300L)/4096 * vcc / 3300; + adc_data.adc_vmeas_b_mv = (adc_aggregate[VMEAS_B]*13300L)/4096 * vcc / 3300; + + buf_a[bufp] = adc_data.adc_vmeas_a_mv; + buf_b[bufp] = adc_data.adc_vmeas_b_mv; + if (++bufp >= sizeof(buf_a)/sizeof(buf_a[0])) { + bufp = 0; + } + + count = 0; + for (int i=0; i<NCH; i++) + adc_aggregate[i] = 0; + } +} + |