ESP32 Forum

Posted: **Thu Jul 28, 2022 6:45 am**

Hello

I am using ESP32 S3 with GATT server example. When I am sending read characteristic request from BLE client (ESP32 S3) then I am getting proper response as shown

: BLE client log from ESP32 S3; ble_c_resp.PNG (29.92 KiB) Viewed 2883 times

But same request is sent form mobile app then I am getting same hex value dumped over 4-5 times and getting warning in the logs of my ESP32 S3 GATT SERVER

: BLE Server log in ESP32 S3 when requested from app; ble.PNG (37.64 KiB) Viewed 2883 times

BLE server code snippet :

Code: Select all

#define GATTS_DEMO_CHAR_VAL_LEN_MAX 0xf0
static uint8_t BLE_payload[60] =  { 46, 197, 213, 196, 245,  22,  22,  98,130, 180, 185,  27, 212,  55, 243, 215, 135,  12,   2,  75,  16,  54, 218, 125, 183, 159,  35, 161, 215, 221,  97, 26, 110, 105,  64, 145, 228, 242,  80,  70, 156,  34, 121, 213,  49, 229, 199, 148, 134, 73};
static uint8_t BLE_buffer[22] = { 46, 197, 213, 196, 245, 22, 22, 98, 130, 180, 185, 27, 212, 55, 243, 215, 135, 12, 2, 75, 16 };
static esp_attr_value_t gatts_demo_char1_val =
{
    .attr_max_len = GATTS_DEMO_CHAR_VAL_LEN_MAX,
    .attr_len     = 60,
    .attr_value   = BLE_payload,
};

Code: Select all

  
    case ESP_GATTS_READ_EVT: {
        ESP_LOGI(GATTS_TAG, "GATT_READ_EVT, conn_id %d, trans_id %d, handle %d\n", param->read.conn_id, param->read.trans_id, param->read.handle);
        esp_gatt_rsp_t rsp;
        memset(&rsp, 0, sizeof(esp_gatt_rsp_t));
        rsp.attr_value.handle = param->read.handle;
        rsp.attr_value.len = 32;
        rsp.attr_value.value[0] = 0xde;
        rsp.attr_value.value[1] = 0xed;
        rsp.attr_value.value[2] = 0xbe;
        rsp.attr_value.value[3] = 0xef;
	    memcpy(rsp.attr_value.value, BLE_payload, 32);
        esp_ble_gatts_send_response(gatts_if, param->read.conn_id, param->read.trans_id,
                                    ESP_GATT_OK, &rsp);
        break;

Response observed on app

: Screenshot from NRF connect app after sending read request; nrf_ss.jpeg (157.7 KiB) Viewed 2883 times

Posted: **Mon Aug 01, 2022 6:09 am**

I didnt check your code, but from NRF connect screenshot i can tell that you are sending incorrect value (characteristic value) on CCC descriptor request.

Posted: **Mon Aug 01, 2022 6:19 am**

Yes, but that is not the case with same data, wen requested from ESP module instead of the app

Posted: **Mon Aug 01, 2022 6:29 am**

1. your code is messed in many places, one i mentioned above, another is probably sending response on read request, which is not setting bit which tells its not whole value sent (due to MTU size)
2. i am guessing esp32 BLE client code is exchanging MTU with server code, which you are not doing when using NRF connect app; this has to be done manually

All above are only guessing, because there is not enough info to provide more accurate solution.

Posted: **Tue Aug 02, 2022 5:57 am**

chegewara wrote: ↑
Mon Aug 01, 2022 6:29 am
1. your code is messed in many places, one i mentioned above, another is probably sending response on read request, which is not setting bit which tells its not whole value sent (due to MTU size)
2. i am guessing esp32 BLE client code is exchanging MTU with server code, which you are not doing when using NRF connect app; this has to be done manually

All above are only guessing, because there is not enough info to provide more accurate solution.

Even if I use GATT server example as it is, I am not able to increase response bytes greater than 22. Or I don't know how to do that properly.
I want to send 60-70 bytes of data, Is there any way to manage this payload size ?

Posted: **Tue Aug 02, 2022 6:29 am**

: Screenshot_20220802-082708_nRF Connect.jpg (231.93 KiB) Viewed 2723 times

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