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Added running variance calculation and report of stdev to remote LC messages #278

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Added running variance calculation and report of stdev to remote LC messages #278

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42 changes: 37 additions & 5 deletions src/lib/sensor_sampler/loadCellSampler.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,11 @@ static bool loadCellSample() {
float calFactor = _loadCell->getCalibrationFactor();
int32_t zeroOffset = _loadCell->getZeroOffset();

float running_mean = 0;
float running_var = 0;
float old_mean = 0;
float stdev = 0;
Comment on lines +53 to +56
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@matt001k matt001k Apr 14, 2025

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These values will be reset to zero every time this function is ran. To avoid this create a variable that will be static. That way the value is retained every time this function is ran. Note how max_force, min_force and mean_force are all static variables.


RTCTimeAndDate_t timeAndDate;
char rtcTimeBuffer[32];
if (rtcGet(&timeAndDate) == pdPASS) {
Expand All @@ -61,6 +66,8 @@ static bool loadCellSample() {
}
successful_lc_read = false;
read_start_time = uptimeGetMicroSeconds() / 1000;

//load cell read attempt block
while ((!successful_lc_read) &&
(((uptimeGetMicroSeconds() / 1000) - read_start_time) < read_attempt_duration)) {
if (_loadCell->available()) {
Expand All @@ -84,10 +91,15 @@ static bool loadCellSample() {
printf("%llu | calFactor: %f\n", uptimeGetMicroSeconds() / 1000, calFactor);
printf("%llu | zeroOffset: %d\n", uptimeGetMicroSeconds() / 1000, zeroOffset);
successful_lc_read = true;

} else {
vTaskDelay(pdMS_TO_TICKS(10));
}
}

//___________________________________________________________________________
//steps that happen every read

cellular_send_read_counter++;
if (weight < min_force) {
min_force = weight;
Expand All @@ -97,17 +109,33 @@ static bool loadCellSample() {
}
mean_sum += weight;

//running variance block
old_mean = running_mean;
running_mean = running_mean + ((weight - running_mean)/cellular_send_read_counter);
running_var = running_var + ((weight - running_mean)*(weight - old_mean));


//___________________________________________________________________________


// Message send block once all the readings are taken.
if (cellular_send_read_counter % num_reads == 0) {
printf("\n\n\n\nThis should only print once every 4 mins\n\n\n");
mean_force = mean_sum / cellular_send_read_counter;

printf("mean force: %f | max force: %f | min force: %f\n\n\n", mean_force, max_force,
min_force);

char data_string[100];
running_var = running_var/cellular_send_read_counter;
stdev = sqrtf(running_var);

printf("Loadcell | mean force: %f | max force: %f | min force: %f | stdev: %f | reading count: %d", mean_force,
max_force, min_force, stdev, cellular_send_read_counter);

char data_string[200];
memset(data_string, 0, sizeof(data_string));


sprintf(data_string, "mean force: %f | max force: %f | min force: %f", mean_force,
max_force, min_force);
sprintf(data_string, "Loadcell | mean force: %f | max force: %f | min force: %f | stdev: %f | reading count: %d", mean_force,
max_force, min_force, stdev, cellular_send_read_counter);

Comment on lines +137 to 139
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@matt001k matt001k Apr 14, 2025

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I recommend using snprintf here to avoid a buffer overflow of data_string. There also is some optimization if you make data_string a static variable. This way, the memory is allocated at compile time rather than every time this function is ran, saving you processing cycles and task memory usage.

spotter_tx_data(data_string, 100, BmNetworkTypeCellularIriFallback);

Expand All @@ -118,6 +146,10 @@ static bool loadCellSample() {
max_force = 0;
min_force = 10000;
mean_force = 0;
running_mean = 0;
running_var = 0;
old_mean = 0;
stdev = 0;
}

return rval;
Expand Down