From ddbb807e54245bd5b6686096827f4124ef196957 Mon Sep 17 00:00:00 2001
From: jaseg <git@jaseg.net>
Date: Tue, 17 Apr 2018 11:56:09 +0200
Subject: Move to new serial protocol.

This code is tested.
---
 firmware/adc.c | 101 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 firmware/adc.c

(limited to 'firmware/adc.c')

diff --git a/firmware/adc.c b/firmware/adc.c
new file mode 100644
index 0000000..02517a7
--- /dev/null
+++ b/firmware/adc.c
@@ -0,0 +1,101 @@
+/* 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 <stm32f0xx.h>
+#include <stdint.h>
+#include <system_stm32f0xx.h>
+#include <stm32f0xx_ll_utils.h>
+#include <math.h>
+
+#include "adc.h"
+
+volatile int16_t adc_vcc_mv = 0;
+volatile int16_t adc_temp_celsius = 0;
+
+static volatile uint16_t adc_buf[2];
+
+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 the slowest available sample rate */
+    ADC1->SMPR  = (7<<ADC_SMPR_SMP_Pos);
+    /* Internal VCC and temperature sensor channels */
+    ADC1->CHSELR = 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 = sizeof(adc_buf)/sizeof(adc_buf[0]);
+    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);
+}
+
+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[2] = {0, 0}; /* oversampling accumulator */
+
+    /* Clear the interrupt flag */
+    DMA1->IFCR |= DMA_IFCR_CGIF1;
+
+    adc_aggregate[0] += adc_buf[0];
+    adc_aggregate[1] += adc_buf[1];
+
+    if (++count == (1<<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_vcc_mv = (3300 * VREFINT_CAL)/(adc_aggregate[0]>>ADC_OVERSAMPLING);
+        int32_t temperature = (((uint32_t)TS_CAL1) - ((adc_aggregate[1]>>ADC_OVERSAMPLING) * adc_vcc_mv / 3300)) * 1000;
+        temperature = (temperature/5336) + 30;
+        adc_temp_celsius = temperature;
+
+        count = 0;
+        adc_aggregate[0] = 0;
+        adc_aggregate[1] = 0;
+    }
+}
+
-- 
cgit