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Fix negative watt values #5

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merged 3 commits into from Sep 5, 2022
Merged

Fix negative watt values #5

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903694c
Fix negative watt values
dailow May 17, 2022
1a4411e
Fix 1's coplement negative processing
jrouvier Sep 5, 2022
715bc99
Negative number handling syntax
jrouvier Sep 5, 2022
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15 changes: 13 additions & 2 deletions src/emporia_vue_utility.h
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Expand Up @@ -297,16 +297,27 @@ class EmporiaVueUtility : public Component, public UARTDevice {
int32_t watts;

// Read the instant watts value
watts = bswap32(mr->watts);
// (it's actually a 24-bit int)
watts = (bswap32(mr->watts) & 0xFFFFFF);

// Bit 1 of the left most byte indicates a negative value
if (watts & 0x800000) {
if (watts == 0x800000) {
// Exactly "negative zero", which means "missing data"
ESP_LOGI(TAG, "Instant Watts value missing");
return;
} else if (watts & 0xC00000) {
// This is either more than 12MW being returned,
// or it's a negative number in 1's complement.
// Since the returned value is a 24-bit value
// and "watts" is a 32-bit signed int, we can
// get away with this.
watts -= 0xFFFFFF;
} else {
// If we get here, then hopefully it's a negative
// number in signed magnitude format
watts = (watts ^ 0x800000) * -1;
}
watts -= 0x800000;
}

if ((watts >= WATTS_MAX) || (watts < WATTS_MIN)) {
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