sd_ble_gattc_exchange_mtu_request()

uint32_t sd_ble_gattc_exchange_mtu_request	(	uint16_t	conn_handle,
		uint16_t	client_rx_mtu )

#include <ble_gattc.h>

Start an ATT_MTU exchange by sending an Exchange MTU Request to the server.

The SoftDevice sets ATT_MTU to the minimum of:

• The Client RX MTU value, and
• The Server RX MTU value from BLE_GATTC_EVT_EXCHANGE_MTU_RSP.

However, the SoftDevice never sets ATT_MTU lower than BLE_GATT_ATT_MTU_DEFAULT.

Events generated

BLE_GATTC_EVT_EXCHANGE_MTU_RSP

Relevant Message Sequence Charts

GATTC ATT_MTU Exchange

Parameters

[in]	conn_handle	The connection handle identifying the connection to perform this procedure on.
[in]	client_rx_mtu	Client RX MTU size. The minimum value is BLE_GATT_ATT_MTU_DEFAULT. The maximum value is ble_gatt_conn_cfg_t::att_mtu in the connection configuration used for this connection. The value must be equal to Server RX MTU size given in sd_ble_gatts_exchange_mtu_reply if an ATT_MTU exchange has already been performed in the other direction.

Return values

NRF_SUCCESS	Successfully sent request to the server.
BLE_ERROR_INVALID_CONN_HANDLE	Invalid connection handle.
NRF_ERROR_INVALID_STATE	Invalid connection state or an ATT_MTU exchange was already requested once.
NRF_ERROR_INVALID_PARAM	Invalid Client RX MTU size supplied.
NRF_ERROR_BUSY	Client procedure already in progress.
NRF_ERROR_TIMEOUT	There has been a GATT procedure timeout. No new GATT procedure can be performed without reestablishing the connection.