I figured out the problem. In the call to esp_ble_gattc_get_characteristic() I was passing in p_data->search_res.srvc_id for the srvc_id param, the correct srvc_id to use is p_data->get_char.srvc_id.

I am using the example gatt_client from the espressif github: https://github.com/espressif/esp-idf/tree/master/examples/bluetooth/gatt_client I just modified the ESP_GAP_BLE_SCAN_RESULT_EVT() callback to look for my peripheral and connect to it, everything else is the same. What is interesting is th...

From what I understand the esp_ble_gattc_get_characteristic() is called with start_char_id = NULL to get the first characteristic, and then in the callback ESP_GATTC_GET_CHAR_EVT , esp_ble_gattc_get_characteristic() is called again with start_char_id = char_id received to get the next characteristic...