ADC working

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;
+    }
+}
+