aboutsummaryrefslogtreecommitdiff
path: root/fw/adc.c
diff options
context:
space:
mode:
authorjaseg <git@jaseg.net>2018-12-23 12:57:40 +0900
committerjaseg <git@jaseg.net>2018-12-23 12:57:40 +0900
commit62389e00fed49b7b89f465c9cd6bb586502331be (patch)
treee38348acaef07b595459057422ee6d92f8cea9c8 /fw/adc.c
parent468fe59d9747078830dd489668b8c8ee8520b4a5 (diff)
download8seg-62389e00fed49b7b89f465c9cd6bb586502331be.tar.gz
8seg-62389e00fed49b7b89f465c9cd6bb586502331be.tar.bz2
8seg-62389e00fed49b7b89f465c9cd6bb586502331be.zip
ADC working
Diffstat (limited to 'fw/adc.c')
-rw-r--r--fw/adc.c118
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;
+ }
+}
+