From 38f40034b0a200586429a3d8329479ad13d84d94 Mon Sep 17 00:00:00 2001 From: Riku Isokoski Date: Fri, 2 Jul 2021 18:30:32 +0300 Subject: Float voltage to int (#444) * Change voltage float to millivolt integer * Explain the ADC to milliVolts conversion --- src/components/battery/BatteryController.cpp | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) (limited to 'src/components/battery/BatteryController.cpp') diff --git a/src/components/battery/BatteryController.cpp b/src/components/battery/BatteryController.cpp index b153b980..02901dd8 100644 --- a/src/components/battery/BatteryController.cpp +++ b/src/components/battery/BatteryController.cpp @@ -55,17 +55,21 @@ void Battery::SaadcInit() { void Battery::SaadcEventHandler(nrfx_saadc_evt_t const* p_event) { - const float battery_max = 4.18; // maximum voltage of battery ( max charging voltage is 4.21 ) - const float battery_min = 3.20; // minimum voltage of battery before shutdown ( depends on the battery ) + const uint16_t battery_max = 4180; // maximum voltage of battery ( max charging voltage is 4.21 ) + const uint16_t battery_min = 3200; // minimum voltage of battery before shutdown ( depends on the battery ) if (p_event->type == NRFX_SAADC_EVT_DONE) { APP_ERROR_CHECK(nrfx_saadc_buffer_convert(&saadc_value, 1)); - voltage = (static_cast(p_event->data.done.p_buffer[0]) * 2.04f) / (1024 / 3.0f); - voltage = roundf(voltage * 100) / 100; + // A hardware voltage divider divides the battery voltage by 2 + // ADC gain is 1/5 + // thus adc_voltage = battery_voltage / 2 * gain = battery_voltage / 10 + // reference_voltage is 0.6V + // p_event->data.done.p_buffer[0] = (adc_voltage / reference_voltage) * 1024 + voltage = p_event->data.done.p_buffer[0] * 6000 / 1024; - percentRemaining = static_cast(((voltage - battery_min) / (battery_max - battery_min)) * 100); + percentRemaining = (voltage - battery_min) * 100 / (battery_max - battery_min); percentRemaining = std::max(percentRemaining, 0); percentRemaining = std::min(percentRemaining, 100); -- cgit v1.2.3-70-g09d2