feat(tempdeck-gen3): use updated peltier current readback function (#438

)

* Updated current measurement transfer function

stm32-modules/include/tempdeck-gen3/tempdeck-gen3/thermal_task.hpp

@@ -53,26 +53,25 @@ struct Peltier {
 // Provides constants & conversions for the internal ADC
 struct PeltierReadback {
     // Internal ADC max value is 12 bits = 0xFFF = 4095
-    static constexpr double MAX_ADC_COUNTS = 4095;
+    static constexpr double MAX_ADC_COUNTS = 4096;
     // Internal ADC is scaled to 3.3v max
     static constexpr double MAX_ADC_VOLTAGE = 3.3;
-    // Voltage for current measurement is amplified by 50x
-    static constexpr double CURRENT_AMP_GAIN = 50;
-    // Current measurement resistor is 10 milliohms = 0.001
-    static constexpr double CURRENT_AMP_RESISTOR_OHMS = 0.01;
-    // Milliamps per ampere
-    static constexpr double MILLIAMPS_PER_AMP = 1000.0;
+    // Amps per volt based on schematic
+    static constexpr double MILLIAMPS_PER_VOLT = 3773;
+    // Constant offset C for a y = mx + b regression
+    static constexpr double MILLIAMP_OFFSET = -6225;
     // Final conversion factor between adc and current
     static constexpr double MILLIAMPS_PER_COUNT =
-        ((MAX_ADC_VOLTAGE * MILLIAMPS_PER_AMP) /
-         (MAX_ADC_COUNTS * CURRENT_AMP_GAIN * CURRENT_AMP_RESISTOR_OHMS));
+        ((MAX_ADC_VOLTAGE * MILLIAMPS_PER_VOLT) / MAX_ADC_COUNTS);
 
     static auto adc_to_milliamps(uint32_t adc) -> double {
-        return static_cast<double>(adc) * MILLIAMPS_PER_COUNT;
+        return (static_cast<double>(adc) * MILLIAMPS_PER_COUNT) +
+               MILLIAMP_OFFSET;
     }
 
     static auto milliamps_to_adc(double milliamps) -> uint32_t {
-        return static_cast<uint32_t>(milliamps / MILLIAMPS_PER_COUNT);
+        return static_cast<uint32_t>((milliamps - MILLIAMP_OFFSET) /
+                                     MILLIAMPS_PER_COUNT);
     }
 };
 

stm32-modules/tempdeck-gen3/firmware/thermistor/internal_adc_hardware.c

@@ -169,6 +169,8 @@ static void init_adc_hardware(ADC_HandleTypeDef *handle) {
         ret = HAL_ADC_ConfigChannel(handle, &channel_config);
         configASSERT(ret == HAL_OK);
     }
+
+    HAL_ADCEx_Calibration_Start(handle, ADC_SINGLE_ENDED);
 }
 
 static void init_dma_hardware(void)

stm32-modules/tempdeck-gen3/tests/test_thermal_task.cpp

@@ -4,17 +4,23 @@
 
 TEST_CASE("peltier current conversions") {
     GIVEN("some ADC readings") {
-        std::vector<uint32_t> inputs = {0, 100, 1000};
+        const auto COUNT = 4;
+        std::vector<uint32_t> inputs = {0, 1000, 4095, 2048};
+        std::vector<double> expected = {-6225, -3185.23, 6222.86, 0.45};
         WHEN("converting readings") {
-            std::vector<double> outputs(3);
+            std::vector<double> outputs(COUNT);
             std::transform(inputs.begin(), inputs.end(), outputs.begin(),
                            thermal_task::PeltierReadback::adc_to_milliamps);
             THEN("the readings are converted correctly") {
-                std::vector<double> expected = {0, 161.172, 1611.722};
-                REQUIRE_THAT(outputs, Catch::Matchers::Approx(expected));
+                for (auto i = 0; i < COUNT; ++i) {
+                    DYNAMIC_SECTION("reading " << i) {
+                        REQUIRE_THAT(outputs[i], Catch::Matchers::WithinAbs(
+                                                     expected[i], 0.1));
+                    }
+                }
             }
             AND_THEN("backconverting readings") {
-                std::vector<uint32_t> backconvert(3);
+                std::vector<uint32_t> backconvert(COUNT);
                 std::transform(outputs.begin(), outputs.end(),
                                backconvert.begin(),
                                thermal_task::PeltierReadback::milliamps_to_adc);
@@ -579,6 +585,9 @@ TEST_CASE("thermal task offset constants message handling") {
 TEST_CASE("thermal task power debug functionality") {
     auto *tasks = tasks::BuildTasks();
     TestThermalPolicy policy;
+    const double peltier_leeway =
+        std::abs(thermal_task::PeltierReadback::adc_to_milliamps(1) -
+                 thermal_task::PeltierReadback::adc_to_milliamps(3));
     const double peltier_current = GENERATE(200.0F, 2000.0F, 0.0F);
     auto current_adc =
         thermal_task::PeltierReadback::milliamps_to_adc(peltier_current);
@@ -616,11 +625,9 @@ TEST_CASE("thermal task power debug functionality") {
                     std::get<messages::GetThermalPowerDebugResponse>(
                         response_msg);
                 REQUIRE(response.responding_to_id == power_msg.id);
-                // There has to be a fair amount of leeway here because the
-                // accuracy of the conversions isn't the best
                 REQUIRE_THAT(response.peltier_current,
                              Catch::Matchers::WithinAbs(peltier_current,
-                                                        peltier_current * .01));
+                                                        peltier_leeway));
                 REQUIRE_THAT(response.peltier_pwm,
                              Catch::Matchers::WithinAbs(0, .01));
                 REQUIRE_THAT(response.fan_pwm,
@@ -659,11 +666,9 @@ TEST_CASE("thermal task power debug functionality") {
                         std::get<messages::GetThermalPowerDebugResponse>(
                             response_msg);
                     REQUIRE(response.responding_to_id == power_msg.id);
-                    // There has to be a fair amount of leeway here because the
-                    // accuracy of the conversions isn't the best
                     REQUIRE_THAT(response.peltier_current,
-                                 Catch::Matchers::WithinAbs(
-                                     peltier_current, peltier_current * .01));
+                                 Catch::Matchers::WithinAbs(peltier_current,
+                                                            peltier_leeway));
                     REQUIRE_THAT(
                         response.peltier_pwm,
                         Catch::Matchers::WithinAbs(peltier_msg.power, .001));