BLE cannot send the correct temperature measurement char value 0x2A1C

[StevenW807]

Hi,
Hardware (BLE server): ESP32-C3-DevKitM-1
Mobile App (BLE client): nRF Connect
Example code: Gatt_Server_Service_Table

I would like to BLE standard Environmental Sensing Service (ESS 0x181A), Temperature Measurement Characteristic (0x2A1C)

How to send the temperature float value such as 25.63℃ in the correct format? If I use uint8_t ess_temperature[] = {0x00, 0x03, 0x0A, 0x00,0x00}; It will show 2563.00℃, but I want to show 25.63℃.

Code: Select all

[Codebox=c file=Untitled.c]
enum{
	ESS_SERVICE,

	ESS_TEMPERATURE_CHAR,
	ESS_TEMPERATURE_VALUE,
	ESS_TEMPERATURE_CFG,

	ESS_HUMIDITY_SERVICE,
	ESS_HUMIDITY_VAL,
	ESS_HUMIDITY_CFG,

	ESS_IDX_NB,
};

// =============== ESS Service ===============
static const uint16_t GATTS_SERVICE_UUID_ESS      			= 0x181A;
static const uint16_t GATTS_CHAR_UUID_ESS_TEMPERATURE   	= 0x2A1C;
static const uint16_t GATTS_CHAR_UUID_ESS_HUMIDITY   		= 0x2A6F;
//static const uint8_t ess_temperature[2]      				= {0x19, 0x05};   	// = 25.5 degC
// static const uint8_t ess_temperature_ccc[2]     			= {0x00, 0x00};
//static const uint8_t ess_humidity[2]      					= {0x0B, 0x05};		// = 11.5%
// static const uint8_t ess_humidity_ccc[2]     			= {0x00, 0x00};
uint8_t ess_temperature[5] = {0x00,0x41, 0x33, 0xB9, 0xD7};
static const uint16_t ess_humidity = 3556;     // nRF Connect App will divide this value by 100. For example, if we use 3654, App will show 36.54% humidity



static const esp_gatts_attr_db_t ess_gatt_db[ESS_IDX_NB] =
{
		[ESS_SERVICE]        =
		{{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_16, (uint8_t *)&primary_service_uuid, ESP_GATT_PERM_READ,
		sizeof(uint16_t), sizeof(GATTS_SERVICE_UUID_ESS), (uint8_t *)&GATTS_SERVICE_UUID_ESS}},

		// Temperature -------------------------------------------------
		[ESS_TEMPERATURE_CHAR]     =
		{{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_16, (uint8_t *)&character_declaration_uuid, ESP_GATT_PERM_READ,
		CHAR_DECLARATION_SIZE, CHAR_DECLARATION_SIZE, (uint8_t *)&char_prop_read}},

		[ESS_TEMPERATURE_VALUE] =
		{{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_16, (uint8_t *)&GATTS_CHAR_UUID_ESS_TEMPERATURE, ESP_GATT_PERM_READ,
		GATTS_DEMO_CHAR_VAL_LEN_MAX, sizeof(ess_temperature), (uint8_t *)&ess_temperature}},

		[ESS_TEMPERATURE_CFG]  =
		{{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_16, (uint8_t *)&character_client_config_uuid, ESP_GATT_PERM_READ | ESP_GATT_PERM_WRITE,
		sizeof(uint16_t), sizeof(cccd_disable_notify_indicate), (uint8_t *)cccd_disable_notify_indicate}},

		// Humidity -------------------------------------------
		[ESS_HUMIDITY_SERVICE]      =
		{{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_16, (uint8_t *)&character_declaration_uuid, ESP_GATT_PERM_READ,
		CHAR_DECLARATION_SIZE, CHAR_DECLARATION_SIZE, (uint8_t *)&char_prop_read}},

		[ESS_HUMIDITY_VAL]  =
		{{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_16, (uint8_t *)&GATTS_CHAR_UUID_ESS_HUMIDITY, ESP_GATT_PERM_READ,
		GATTS_DEMO_CHAR_VAL_LEN_MAX, sizeof(ess_humidity), (uint8_t *)&ess_humidity}},

		[ESS_HUMIDITY_CFG]  =
		{{ESP_GATT_AUTO_RSP}, {ESP_UUID_LEN_16, (uint8_t *)&character_client_config_uuid, ESP_GATT_PERM_READ | ESP_GATT_PERM_WRITE,
		sizeof(uint16_t), sizeof(cccd_disable_notify_indicate), (uint8_t *)cccd_disable_notify_indicate}},
};
[/Codebox]

But on nRF Connect App in mobile phone, it shows the result is -0.00℃. How to send the temperature float value such as 25.6℃ in the correct format?

111.png (117.39 KiB) Viewed 483 times

Thanks