Reading a voltage - I don't know the syntax for displaying it in an object

[richardsg307]

I've compiled my own OpenHasp for a Guition 4848S040 using GitPod. It reads the Battery voltage using an ADC on GPIO 1. It seems to work as I can see the voltage in MQTT Explorer (vbat_Fraction and vbat_Level).

Here's the my_custom.cpp code.

/* MIT License - Copyright (c) 2019-2024 Francis Van Roie
   For full license information read the LICENSE file in the project folder */

// USAGE: - Copy this file and rename it to my_custom.cpp
//         - Change false to true on line 9

#include "hasplib.h"

#if defined(HASP_USE_CUSTOM) && HASP_USE_CUSTOM > 0 && true // <-- set this to true in your code

#include "hasp_debug.h"

unsigned long last_blink = 0;
const int voltage_read = 1; // GPIO 1 can do ADC
const int blink_speed = 10000; // Every 10 seconds

float batteryFraction;
float voltageLevel;
int vbat;

// Voltage read
const int MAX_ANALOG_VAL = 4095;
const float MAX_BATTERY_VOLTAGE = 4.2; // Typical Max of a LiPo


void custom_setup()
{
    // Initialization code here
    last_blink = millis();
    pinMode(voltage_read, INPUT);
    randomSeed(millis());
}

void custom_loop()
{
    // Non-blocking code here, this should execute very fast!
    if(blink_speed && (millis() - last_blink > blink_speed)){
        vbat = analogRead(voltage_read);
        voltageLevel = (vbat / 4095.0 * 4.2);
        batteryFraction = voltageLevel / MAX_BATTERY_VOLTAGE;
        last_blink = millis();
    }
}

void custom_every_second()
{
    Serial.print("#");
}

void custom_every_5seconds()
{
    LOG_VERBOSE(TAG_CUSTOM, "5 seconds have passsed...");
    String vbatFraction = String(batteryFraction);
    String vbatLevel = String(voltageLevel);
 
    String jsonStringL = "{\"vbat_Level\":" + vbatLevel + "}";
    String jsonStringF = "{\"vbat_Fraction\":" + vbatFraction + "}";
    const char* jsonCharL = jsonStringL.c_str();
    const char* jsonCharF = jsonStringF.c_str();

    dispatch_state_subtopic("vbat_Fraction", jsonCharF);
    dispatch_state_subtopic("vbat_Level", jsonCharL);
    
}

bool custom_pin_in_use(uint8_t pin)
{
    if(pin == 1) return true;  // This is the only GPIO I use here
    // otherwise the pin is not used
    return false;
}

void custom_get_sensors(JsonDocument& doc)
{
    /* Sensor Name */
    JsonObject sensor = doc.createNestedObject(F("Custom"));

    /* Key-Value pair of the sensor value */
    sensor[F("Random")] = HASP_RANDOM(256);
}

void custom_topic_payload(const char* topic, const char* payload, uint8_t source){
    // Not used
}

void custom_state_subtopic(const char* subtopic, const char* payload){
    // Not used
}

#endif // HASP_USE_CUSTOM

I don't know what some of it does or why; I just copied and modified examples I found.

A few questions:

1. Am I correct in thinking the vbat_Level and vbat_Fraction exist as Float type data?
2. What is the syntax for referencing it from an OpenHasp Object (ie Gauge or Label)?
3. How can I get them to appear in Home Assistant as an additional Entities to the Device?

Thanks

[fvanroie]

You can include a function to update a label or gauge object like this:

static void custom_label_update(uint8_t page, uint8_t id, String text)
{
    lv_obj_t* label = hasp_find_obj_from_page_id(page, id);
    if(!label) return; // object doesn't exist
    lv_label_set_text(label, text.c_str());  // Use c string function the get the text data only
}

static void custom_gauge_update(uint8_t page, uint8_t id, int32_t val)
{
    lv_obj_t* gauge = hasp_find_obj_from_page_id(page, id);
    if(!gauge) return; // object doesn't exist
    lv_gauge_set_value(gauge, 0, val);  // 0 is the needle id (always use 0)
}

static void custom_read_battery() {
    if(millis() - last_blink >= blink_speed) {   // only update the values every 10 seconds
        vbat = analogRead(voltage_read);
        voltageLevel = (vbat / 4095.0 * 4.2);
        batteryFraction = voltageLevel / MAX_BATTERY_VOLTAGE;
        last_blink = millis();
    }
}

Then you can call them as needed from custom_every_5seconds:

void custom_every_5seconds()
{
    LOG_VERBOSE(TAG_CUSTOM, "5 seconds have passsed...");

    custom_read_battery();
    String vbatFraction = String(batteryFraction);
    String vbatLevel = String(voltageLevel);
 
    // This will update the objects on screen using page number and object id
    custom_label_update(1, 150, vbatFraction);
    custom_label_update(1, 151, vbatLevel );
    int32_t val = vbat *100 / 4095;         // calculate the correct val for the gauge needle
    custom_gauge_update(1, 160, val);     // val depends on the min and max value of the gauge

    // This will publish the data to MQTT, if you don't need that remove this code
    String jsonStringL = "{\"vbat_Level\":" + vbatLevel + "}";
    String jsonStringF = "{\"vbat_Fraction\":" + vbatFraction + "}";
    const char* jsonCharL = jsonStringL.c_str();
    const char* jsonCharF = jsonStringF.c_str();

    dispatch_state_subtopic("vbat_Fraction", jsonCharF);
    dispatch_state_subtopic("vbat_Level", jsonCharL);
}

To make the code run as fast as possible, remove the updating in custom_loop and custom_every_second:

void custom_loop()
{
}

void custom_every_second()
{
}

Only read the GPIO before it's output is actually being used...

openHASP will post to the MQTT sensors subtopic every 30 seconds, you can add the data to that JSON if needed:

void custom_get_sensors(JsonDocument& doc)
{
    custom_read_battery();
    String vbatFraction = String(batteryFraction);
    String vbatLevel = String(voltageLevel);

    /* Sensor Name */
    JsonObject sensor = doc.createNestedObject(F("Battery"));

    /* Key-Value pair of the sensor value */
    sensor[F("Fraction")] = vbatFraction;
    sensor[F("Level")] = vbatLevel;
}

I'm not a Home Assistant expert, but you can verify that the sensor values are available in MQTT using a tool like MQTT Explorer. Then check the Home Assistant guide to use the MQTT values...

Note: This code has not been tested and might need testing or tweaking to get it to compile and work properly, but this should get you on your way to update the objects and post sensor data to MQTT.

[richardsg307]

Thank you for that, I will give it a go.

I was looking for, and had tried, a syntax that just pulled the values into the object in the same way you can pull the IP address ("%ip%") and other parameters listed in documentation (Design/Data Types/Variables). Your method is the code pushing the values. That makes it very cumbersome during the development as each compile can take a while. And it assumes I know what I want the screens to look like. My approach is to try it and modify till I get something I like.

[fvanroie]

Well, that's the way it is setup using custom firmware code... I'm sorry to hear you find this method cumbersome. I can't know what you (or every individual using openHASP) is looking for and accommodate everyone.

You are free to use the project any way you want according to its license. If you want more flexibility, you can always add your own variable and hooks and code. Once you start compiling your own firmware, it's up to you to decide what you want to do with it and how you implement your goals.

There is no %battery% or %val% defined, so that won't work out-of-the-box. That would need to be added in code.
My suggestion above is just the way I would go about it, you are free to come up with alternative solutions.

[richardsg307]

I'm not that clever. And I didn't mean to criticise - Sorry. I think you guys that contribute to all these open projects are great.

Anyway, I've implemented the code as you suggested and it worked first compilation. I'm going to tidy it up and calibrate the ADC Battery reading. I have the display powered by a 3V7 LiPo so need to log the voltages as it runs down. I've also got to do some soldering with a resistor voltage divider. I'm also seeing the battery stuff in the sensors MQTT message now along with the original individual messages.

Here's a screen shot - I need to tidy that up too. Get the screen right and then sort out the code!

When done, I'll post the code to help others going down this path.

Thanks again.

[fvanroie]

No worries, good to hear that the code worked out and you can achieve your goal.

[richardsg307]

My final code with comments to explain what is going on.

/* MIT License - Copyright (c) 2019-2024 Francis Van Roie
   For full license information read the LICENSE file in the project folder */

// USAGE: - Copy this file and rename it to my_custom.cpp
//         - Change false to true on line 9

#include "hasplib.h"

#if defined(HASP_USE_CUSTOM) && HASP_USE_CUSTOM > 0 && true // <-- set this to true in your code

#include "hasp_debug.h"

const int voltage_read = 1; // GPIO 1 can do ADC
const int blink_speed = 10000; // Every 10 seconds

float batteryFraction;
float voltageLevel;
int vbat;

// Voltage read
const int MAX_ANALOG_VAL = 4095;  // 12 bit ADC on ESP32 - Not used!
const float MAX_BATTERY_VOLTAGE = 4.2; // Typical Max of a LiPo

void custom_setup()
{
    // Initialization code here
    pinMode(voltage_read, INPUT); // Declare GPIO 1 as input
}

void custom_loop()
{
    // Loop code here
    // Nothing to do here
}

static void custom_label_update(uint8_t page, uint8_t id, String text) // Routine to update any Label
{
    lv_obj_t* label = hasp_find_obj_from_page_id(page, id); // Get hook for the label in question
    if(!label) return; // object doesn't exist so Return
    lv_label_set_text(label, text.c_str());  // Update label. Use c string function the get the text data only
}

static void custom_gauge_update(uint8_t page, uint8_t id, int32_t val) // Routine to update any Gauge
{
    lv_obj_t* gauge = hasp_find_obj_from_page_id(page, id); // Get hook for the gauge in question
    if(!gauge) return; // object doesn't exist
    lv_gauge_set_value(gauge, 0, val);  // Update the gauge. 0 is the needle id (always use 0)
}

static void custom_read_battery() // Read voltage on ADC and convert to Voltage and Fraction
{
    vbat = analogRead(voltage_read);
    voltageLevel = (vbat / 4095.0 * 4.73); // 4.73 determined after calibration of resistor chain 4k7/10k
                                           // such that actual 4.2V across chain gave 4095 on ADC
    batteryFraction = voltageLevel / MAX_BATTERY_VOLTAGE;
}

void custom_every_second()
{
    // Not needed; 
}

void custom_every_5seconds()
{
    String batIcon = "";  // Create string to hold the Battery state icon
    
    LOG_VERBOSE(TAG_CUSTOM, "5 seconds have passsed..."); // I left this in from the code I copied, but probably unnecessary

    custom_read_battery(); // Read Battery voltage. I used a 4k7 and 10k resistor to divide the battery voltage to a level
                           // readable by the, ADC which peaks (4047) at around 3.2V
    String vbatFraction = String(batteryFraction);
    String vbatLevel = String(voltageLevel);
 
    // This will update the objects on screen using page number and object id
    custom_label_update(3, 150, vbatFraction); // On my display the label to display vbatFraction is on Page 3 id 150
    custom_label_update(3, 151, vbatLevel );  // Page 3 id 151
    int32_t val = voltageLevel * 1000; // Gauge needs an integer so convert to mV and use "format":3
                                       //  to remove the 3 trailing zeros on the gauge to display as V
    custom_gauge_update(3, 160, val);  // On the gauge object min is 0 and max is 5000
    if(voltageLevel > 3.8) batIcon = "\uF2A3"; // Full Battery
      else if(voltageLevel > 3.5) batIcon = "\uF2A2"; // Medium
        else if(voltageLevel > 3.2) batIcon = "\uF2A1"; // Low
          else batIcon = "\uE08E";  // Empty
    custom_label_update(0, 7, batIcon ); // Page 0 id 7

    // This will publish the data to MQTT, as individual messages.
    // with the Topic hasp/tablepad/state/[subtopic]
    // If you don't need that remove this code
    String jsonStringL = "{\"vbat_Level\":" + vbatLevel + "}"; // This prepares the payload
    String jsonStringF = "{\"vbat_Fraction\":" + vbatFraction + "}";
    const char* jsonCharL = jsonStringL.c_str(); // Gets the payload in the correct format
    const char* jsonCharF = jsonStringF.c_str();

    dispatch_state_subtopic("vbat_Level", jsonCharL); // Sends message with (subtopic, payload)
    dispatch_state_subtopic("vbat_Fraction", jsonCharF);
}
bool custom_pin_in_use(uint8_t pin)
{
    if(pin == 1) return true;  // GPIO 1 is the only GPIO I use here
    // otherwise, if the pin is not used
    return false;
}

void custom_get_sensors(JsonDocument& doc)
{
    // As an alternative to sending the values individually as above in the Every 5 seconds routine,
    // This adds the values to a hasp/tablepad/state/sensors message that gets sent every 5 minutes.
    String vbatFraction = String(batteryFraction); // Just use the most recent battery reading
    String vbatLevel = String(voltageLevel);

    // Sensor Name. Introduces a nested level "Battery" in the json payload
    JsonObject sensor = doc.createNestedObject(F("Battery"));

    // Key-Value pair of the sensor value. Add these under Battery
    // The resulting payload will look like
    // {"time":"2025-08-09T18:07:26","uptimeSec":15933,"uptime":"0T04:25:33","Battery":{"Fraction":"0.87","Level":"3.64"}}
    sensor[F("Fraction")] = vbatFraction;
    sensor[F("Level")] = vbatLevel;
}

void custom_topic_payload(const char* topic, const char* payload, uint8_t source){
    // Not used
}

void custom_state_subtopic(const char* subtopic, const char* payload){
    // Not used
}

#endif // HASP_USE_CUSTOM

A few point to note:-

1. When you plug the battery in to the Guition display, it will not turn on until you "kick start" it with USB power!
2. When configuring the display through its web interface, I gave "tablepad" as the MQTT Hostname.
3. To get the battery voltage into Home Assistant I created the mqtt sensor

mqtt:
  sensor:
    - name: "Tablepad Battery Voltage"
      unique_id: sunny_mqtt_82
      state_topic: "hasp/tablepad/state/sensors"
      unit_of_measurement: "V"
      value_template: "{{value_json.Battery.Level}}"

4. A few other files in the Gitpod repository need changing - Just follow the instructions here
5. When using Gitpod, to save the Template files with the proper name (as per the instruction) use Menu (Top Left 3 bars) / File/ Save as. That took me ages to find!

Big thanks to elik745i, who got me started, and fvanroie who filled in the blanks