Add analog readout code for supply monitoring

1 files changed, 90 insertions, 0 deletions

diff --git a/src/glutt-o-logique/analog_input.c b/src/glutt-o-logique/analog_input.c
new file mode 100644
index 0000000..02b0441
--- /dev/null
+++ b/src/glutt-o-logique/analog_input.c
@@ -0,0 +1,90 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Matthias P. Braendli, Maximilien Cuony
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+*/
+
+#include "analog_input.h"
+#include "stm32f4xx_adc.h"
+#include <math.h>
+
+void analog_init(void)
+{
+    // Enable ADC and GPIOA clocks
+    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);
+    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
+
+    // Set Pin PA5 to analog input
+    GPIO_InitTypeDef GPIO_InitStructure;
+    GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AN;
+    GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_5;
+    GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_NOPULL;
+    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
+    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
+    GPIO_Init(GPIOC, &GPIO_InitStructure);
+
+    // Init ADC1 for supply measurement
+    ADC_CommonInitTypeDef ADC_CommonInitStruct;
+
+    ADC_CommonInitStruct.ADC_Mode = ADC_Mode_Independent;
+    ADC_CommonInitStruct.ADC_Prescaler = ADC_Prescaler_Div8;
+    ADC_CommonInitStruct.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;
+    ADC_CommonInitStruct.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;
+    ADC_CommonInit(&ADC_CommonInitStruct);
+
+    ADC_InitTypeDef ADC_InitStruct;
+    ADC_InitStruct.ADC_Resolution = ADC_Resolution_12b;
+    ADC_InitStruct.ADC_ScanConvMode = DISABLE;
+    ADC_InitStruct.ADC_ContinuousConvMode = DISABLE;
+    ADC_InitStruct.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
+    ADC_InitStruct.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1;
+    ADC_InitStruct.ADC_DataAlign = ADC_DataAlign_Right;
+    ADC_InitStruct.ADC_NbrOfConversion = 1;
+    ADC_Init(ADC1, &ADC_InitStruct);
+
+    // Configure ADC1 to use the converted 12V signal (see schematics)
+    const uint8_t rank = 1;
+    ADC_RegularChannelConfig(ADC1,
+            ADC_Channel_5,
+            rank,
+            ADC_SampleTime_480Cycles);
+
+    // Enable ADC
+    ADC_Cmd(ADC1, ENABLE);
+}
+
+float analog_measure_12v(void)
+{
+    ADC_SoftwareStartConv(ADC1); //Start the conversion
+
+    // TODO add timeout
+    while (ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET);
+
+    const float raw_value = ADC_GetConversionValue(ADC1);
+
+    // Voltage divider 22k / (82k + 22k) must be inverted here
+    // Also, we round to steps of 0.5
+    float temp = raw_value * (2.0f * 104.0f / 22.0f);
+    temp = roundf(temp);
+    temp = sqrtf(temp);
+    temp = temp / 2.0f;
+    return temp;
+}