RE: How to read from a characteristic which does not have a notify characteristic property?

VinayakaKS — Mon, 05 Aug 2024 09:39:09 GMT

I used a NRF_BLE_GQ_REQ_GATTC_READ for the gattc request and it started working.

Thank you,

Vinayaka KS

RE: How to read from a characteristic which does not have a notify characteristic property?

VinayakaKS — Fri, 05 Jul 2024 06:35:21 GMT

I will have a look into this function, and check if I can read.

Thanks for the info.

Regards,

Vinayaka

RE: How to read from a characteristic which does not have a notify characteristic property?

Vidar Berg — Thu, 04 Jul 2024 11:14:06 GMT

Hi Vinayaka,

You can use sd_ble_gattc_read() as illustrated by the message sequence chart "GATTC Characteristic or Descriptor Value Read". There aren't any GATT client implementations in the SDK that use this function. Grepping through the SDK only gave me the following results:

examples/ble_central_and_peripheral/experimental/ble_app_interactive/cli_m.c:    err_code = sd_ble_gattc_read(conn_handle, val_handle, 0);
examples/ble_central_and_peripheral/experimental/ble_app_interactive/ble_m.c:                err_code = sd_ble_gattc_read(conn_handle, p_service[i].handle_range.start_handle, 0);
examples/ble_central_and_peripheral/experimental/ble_app_interactive/ble_m.c:                err_code = sd_ble_gattc_read(conn_handle, m_srv_char.char_data[i].decl_handle, 0);
examples/ble_central_and_peripheral/experimental/ble_app_interactive/ble_m.c:                err_code = sd_ble_gattc_read(conn_handle, mp_device_srv[conn_handle]->services[i].handle_range.start_handle, 0);
examples/ble_central_and_peripheral/experimental/ble_app_interactive/ble_m.c:                err_code = sd_ble_gattc_read(conn_handle, m_srv_char.char_data[i].decl_handle, 0);
components/ble/nrf_ble_gq/nrf_ble_gq.c:                err_code = sd_ble_gattc_read(conn_handle,
components/ble/nrf_ble_gq/nrf_ble_gq.c:            err_code = sd_ble_gattc_read(conn_handle,
components/ble/peer_manager/gatt_cache_manager.c:                    ret_code_t err_code = sd_ble_gattc_read(conn_handle, *(uint16_t*)p_val->handle_value, 0);
components/serialization/application/codecs/ble/middleware/app_mw_ble_gattc.c:/**@brief Command response callback function for @ref sd_ble_gattc_read BLE command.
components/serialization/application/codecs/ble/middleware/app_mw_ble_gattc.c:#ifndef _sd_ble_gattc_read
components/serialization/application/codecs/ble/middleware/app_mw_ble_gattc.c:#define _sd_ble_gattc_read sd_ble_gattc_read
components/serialization/application/codecs/ble/middleware/app_mw_ble_gattc.c:uint32_t _sd_ble_gattc_read(uint16_t conn_handle,
components/serialization/connectivity/codecs/ble/middleware/conn_mw_ble_gattc.c:    sd_err_code = sd_ble_gattc_read(conn_handle, handle, offset);

The key thing is to find the attribute handle value you want to read from. This is found during the Service discovery procedure.

Best regards,

Vidar