toaster-oven-bluepill/Core/Src/app_analog.c

/**
 * TODO file description
 */

#include "main.h"
#include <stdbool.h>
#include <stdint.h>
#include <string.h>
#include "app_analog.h"
#include "adc.h"

/* DMA dest */
static volatile uint16_t adc_values[4];

const float V_REFINT = 1.23f;

#define AVERAGEBUF_DEPTH 16
#define OVENTEMP_HISTORY_DEPTH 10

static struct App {
  float oven_temp;
  float soc_temp;
  float v_sensor;
  uint16_t adc_averagebuf[AVERAGEBUF_DEPTH * 4];
  uint8_t averagebuf_ptr;
  float adc_averages[4];
  float oventemp_history[OVENTEMP_HISTORY_DEPTH];
  uint8_t oventemp_history_ptr;
} s_analog = {};

#define TSENSE_LOOKUP_LEN 101
#define TSENSE_T_STEP 5.0f
#define TSENSE_T_MIN 0.0f
#define TSENSE_T_MAX 500.0f
static const float TSENSE_LOOKUP[TSENSE_LOOKUP_LEN] = {
        0.092678405931418f,
        0.0943174479327356f,
        0.095948157844312f,
        0.0975706768542549f,
        0.0991848957506647f,
        0.100791037522732f,
        0.102388993070241f,
        0.103978983136042f,
        0.105560980458654f,
        0.107135039851509f,
        0.108701215616829f,
        0.110259642413441f,
        0.111810211533421f,
        0.113353137226489f,
        0.114888310929339f,
        0.11641594480226f,
        0.117936009906507f,
        0.119448557132363f,
        0.120953636903929f,
        0.122451377845456f,
        0.12394167187544f,
        0.125424725109556f,
        0.126900429638119f,
        0.128368989630084f,
        0.129830374697352f,
        0.131284632150064f,
        0.132731808872517f,
        0.134172027901771f,
        0.135605181883591f,
        0.13703146935069f,
        0.138450783142958f,
        0.139863319976468f,
        0.14126904821384f,
        0.142668011892657f,
        0.144060254660872f,
        0.145445894373796f,
        0.146824824486877f,
        0.14819723645253f,
        0.149563023938454f,
        0.150922376699229f,
        0.15227526202401f,
        0.153621720954182f,
        0.15496179417407f,
        0.156295594725426f,
        0.157623016940038f,
        0.158944245649448f,
        0.160259175412251f,
        0.16156798947087f,
        0.162870654195634f,
        0.164167207880495f,
        0.165457688491696f,
        0.166742204592451f,
        0.168020651444079f,
        0.169293207677971f,
        0.170559768793747f,
        0.171820511933356f,
        0.173075402684405f,
        0.174324476817747f,
        0.175567769803026f,
        0.176805386030345f,
        0.178037221732226f,
        0.179263449725904f,
        0.180483966491086f,
        0.181698943447122f,
        0.182908345518766f,
        0.184112206156428f,
        0.185310558533273f,
        0.186503503145257f,
        0.187690937227925f,
        0.188873028139146f,
        0.190049673368296f,
        0.191221038959601f,
        0.192387089280576f,
        0.193547855644572f,
        0.194703369109397f,
        0.195853726532112f,
        0.196998826174689f,
        0.19813883026229f,
        0.199273637315452f,
        0.200403408323351f,
        0.201528107189346f,
        0.20264776325594f,
        0.203762405629782f,
        0.204872127762998f,
        0.205976828960191f,
        0.207076666615101f,
        0.208171540293999f,
        0.209261606226334f,
        0.210346827933364f,
        0.211427232937629f,
        0.212502848543705f,
        0.213573765013592f,
        0.214639882704581f,
        0.215701354457324f,
        0.216758080892489f,
        0.217810213752734f,
        0.218857716249547f,
        0.219900614222686f,
        0.220938933310224f,
        0.221972760781578f,
        0.223001998051553f,
};

void app_analog_init()
{
    HAL_ADCEx_Calibration_Start(&hadc1);

    /* Start periodic reading of the ADC channels */
    HAL_ADC_Start_DMA(&hadc1, (uint32_t *) (void *) adc_values, 4);
}

static float val_to_c(float val)
{
    // TODO use binary search.. lol
    for (int i = 1; i < TSENSE_LOOKUP_LEN; i++) {
        float cur = TSENSE_LOOKUP[i];
        if (cur >= val) {
            float prev = TSENSE_LOOKUP[i - 1];

            float ratio = (val - prev) / (cur - prev);
            return TSENSE_T_MIN + ((float) i + ratio) * TSENSE_T_STEP;
        }
    }
    return TSENSE_T_MAX;
}

float app_analog_get_temp()
{
    uint32_t sums[4] = {};
    for (int i = 0; i < AVERAGEBUF_DEPTH * 4; i += 4) {
        sums[0] += s_analog.adc_averagebuf[i];
        sums[1] += s_analog.adc_averagebuf[i + 1];
        sums[2] += s_analog.adc_averagebuf[i + 2];
        sums[3] += s_analog.adc_averagebuf[i + 3];
    }
    s_analog.adc_averages[0] = (float) sums[0] / AVERAGEBUF_DEPTH;
    s_analog.adc_averages[1] = (float) sums[1] / AVERAGEBUF_DEPTH;
    s_analog.adc_averages[2] = (float) sums[2] / AVERAGEBUF_DEPTH;
    s_analog.adc_averages[3] = (float) sums[3] / AVERAGEBUF_DEPTH;

    /* r_pt100, r_ref, internal_temp, v_ref_int */
    float refint = s_analog.adc_averages[3];
    float scale = V_REFINT / refint;

    const float avg_slope = 4.3f * scale;
    const float v25 = 1.43f;
    const float v_tsen = s_analog.adc_averages[2] * scale;

    s_analog.soc_temp = (v25 - v_tsen) / avg_slope + 25.f;
    s_analog.v_sensor = s_analog.adc_averages[0] * scale; // good for debug/tuning


    // using a voltage divider, so assuming the reference resistor is measured well,
    // we can just use the ratio and the exact voltage value is not important.
    float actual_temp = val_to_c(s_analog.adc_averages[0] / s_analog.adc_averages[1]);

    s_analog.oventemp_history[s_analog.oventemp_history_ptr] = actual_temp;
    s_analog.oventemp_history_ptr = (s_analog.oventemp_history_ptr + 1) % OVENTEMP_HISTORY_DEPTH;

    float sum = 0;
    for (int i = 0; i < OVENTEMP_HISTORY_DEPTH; i++) {
        sum += s_analog.oventemp_history[i];
    }
    sum /= OVENTEMP_HISTORY_DEPTH;
    s_analog.oven_temp = sum;

    return s_analog.oven_temp;
}

void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef *hadc)
{
    // notify
    memcpy((void *) &s_analog.adc_averagebuf[s_analog.averagebuf_ptr * 4], (const void *) adc_values, 8);
    s_analog.averagebuf_ptr = (s_analog.averagebuf_ptr + 1) % AVERAGEBUF_DEPTH;
}