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Add HX711 absolute weight conversion #15292

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Add HX711 absolute weight conversion #15292

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4d57abe
Add HX711 absolute weight conversion
ThomDietrich Apr 4, 2022
b986c06
Merge remote-tracking branch 'origin/development' into hx711-absconv
ThomDietrich Apr 4, 2022
a6f1ed2
Merge remote-tracking branch 'origin/development' into hx711-absconv
ThomDietrich Apr 5, 2022
0981421
Remove memory allocation workaround
ThomDietrich Apr 5, 2022
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38 changes: 32 additions & 6 deletions tasmota/xsns_34_hx711.ino
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,8 @@
#define D_JSON_WEIGHT_CHANGE "WeightChange"
#define D_JSON_WEIGHT_RAW "WeightRaw"
#define D_JSON_WEIGHT_DELTA "WeightDelta"
#define D_JSON_WEIGHT_ABSCONV_A "WeightAbsConvA"
#define D_JSON_WEIGHT_ABSCONV_B "WeightAbsConvB"

enum HxCalibrationSteps { HX_CAL_END, HX_CAL_LIMBO, HX_CAL_FINISH, HX_CAL_FAIL, HX_CAL_DONE, HX_CAL_FIRST, HX_CAL_RESET, HX_CAL_START };

Expand All @@ -73,6 +75,8 @@ struct HX {
long offset = 0;
long scale = 1;
long weight_diff = 0;
long absconv_a = 0;
long absconv_b = 0;
uint8_t type = 1;
uint8_t sample_count = 0;
uint8_t calibrate_step = HX_CAL_END;
Expand Down Expand Up @@ -195,6 +199,8 @@ void SetWeightDelta()
* Sensor34 8 0 - Disable JSON weight change message
* Sensor34 8 1 - Enable JSON weight change message
* Sensor34 9 <weight code> - Set minimum delta to trigger JSON message
* Sensor34 10 <value A> - Set A = a * 10^9 for raw to absolute weight conversion: y=a*x+b
* Sensor34 11 <value B> - Set B = b * 10^6 for raw to absolute weight conversion: y=a*x+b
\*********************************************************************************************/

bool HxCommand(void)
Expand Down Expand Up @@ -259,8 +265,21 @@ bool HxCommand(void)
break;
case 9: // WeightDelta
if (strchr(XdrvMailbox.data, ',') != nullptr) {
Settings->weight_change = strtol(ArgV(argument, 2), nullptr, 10);
SetWeightDelta();
Settings->weight_change = strtol(ArgV(argument, 2), nullptr, 10);
SetWeightDelta();
}
show_parms = true;
break;
case 10: // AbsoluteConversion, A
if (strchr(XdrvMailbox.data, ',') != nullptr) {
Settings->weight_absconv_a = strtol(ArgV(argument, 2), nullptr, 10);
Hx.absconv_a = Settings->weight_absconv_a;
}
show_parms = true;
case 11: // AbsoluteConversion, B
if (strchr(XdrvMailbox.data, ',') != nullptr) {
Settings->weight_absconv_b = strtol(ArgV(argument, 2), nullptr, 10);
Hx.absconv_b = Settings->weight_absconv_b;
}
show_parms = true;
break;
Expand All @@ -272,9 +291,11 @@ bool HxCommand(void)
char item[33];
dtostrfd((float)Settings->weight_item / 10, 1, item);
Response_P(PSTR("{\"Sensor34\":{\"" D_JSON_WEIGHT_REF "\":%d,\"" D_JSON_WEIGHT_CAL "\":%d,\"" D_JSON_WEIGHT_MAX "\":%d,\""
D_JSON_WEIGHT_ITEM "\":%s,\"" D_JSON_WEIGHT_CHANGE "\":\"%s\",\"" D_JSON_WEIGHT_DELTA "\":%d}}"),
Settings->weight_reference, Settings->weight_calibration, Settings->weight_max * 1000,
item, GetStateText(Settings->SensorBits1.hx711_json_weight_change), Settings->weight_change);
D_JSON_WEIGHT_ITEM "\":%s,\"" D_JSON_WEIGHT_CHANGE "\":\"%s\",\"" D_JSON_WEIGHT_DELTA "\":%d,\""
D_JSON_WEIGHT_ABSCONV_A "\":%d,\"" D_JSON_WEIGHT_ABSCONV_B "\":%d}}"),
Settings->weight_reference, Settings->weight_calibration, Settings->weight_max * 1000,
item, GetStateText(Settings->SensorBits1.hx711_json_weight_change), Settings->weight_change,
Settings->weight_absconv_a, Settings->weight_absconv_b);
}

return serviced;
Expand All @@ -301,11 +322,13 @@ void HxInit(void)

SetWeightDelta();

if (HxIsReady(8 * HX_TIMEOUT)) { // Can take 600 milliseconds after power on
if (HxIsReady(8 * HX_TIMEOUT)) { // Can take 600 milliseconds after power on
if (!Settings->weight_max) { Settings->weight_max = HX_MAX_WEIGHT / 1000; }
if (!Settings->weight_calibration) { Settings->weight_calibration = HX_SCALE; }
if (!Settings->weight_reference) { Settings->weight_reference = HX_REFERENCE; }
Hx.scale = Settings->weight_calibration;
if (Settings->weight_absconv_a) { Hx.absconv_a = Settings->weight_absconv_a; }
if (Settings->weight_absconv_b) { Hx.absconv_b = Settings->weight_absconv_b; }
HxRead();
HxResetPart();
Hx.type = 1;
Expand Down Expand Up @@ -451,6 +474,9 @@ void HxShow(bool json)
}
weight = (float)Hx.weight / 1000; // kilograms
}
if (Hx.absconv_a != 0 && Hx.absconv_b != 0) {
weight = (float)Hx.absconv_a / 1e9 * Hx.raw + (float)Hx.absconv_b / 1e6;
}
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Am I right in the conclusion that using the raw value here makes current calibration efforts useless? How do you define the absconv parameters? By trial and error?

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@ThomDietrich ThomDietrich Apr 5, 2022 •
edited
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No you are correct. No offense, but I didn't find the implemented calibration combined with taring the weight upon startup useful for my use case (and wonder in which use case it is). The strategy I follow is to take a few raw weights for known masses, then run a simple linear regression, e.g. here: https://mycurvefit.com to get to the absconv parameters of y=ax+b.
It's not as integrated but is a good deterministic process. Let me know if you believe we should have a discussion about a different path!

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@arendst arendst Apr 7, 2022 •
edited
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My implemented use case is based on a commercial kitchen scale like the Ikea one.

After power on the user adds an empty dish, selects the reset button to zero the result and then is able to weigh anything he adds to the dish. Hence the zero button in the GUI.

There are ofcourse other uses which may use your suggested solution.

As your implementation doesn't interfere with mine I'll add it now so users can get some experience with it.

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Interesting element you brought up!

USE_HX711_GUI is not defined for FIRMWARE_SENSORS. As a result I did never see this "zero button in GUI" you refered to. Maybe this should be changed?

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@arendst ping in case you missed this.

char weight_chr[33];
dtostrfd(weight, Settings->flag2.weight_resolution, weight_chr);

Expand Down