How to increase the packet size for sd_ble_gattc_write

Question

We are using nrf52832 with S132 for our application. 
 Central device connect to Peripheral using sd_ble_gap_connect() api and then uses sd_ble_gattc_write() to write the data. 
 We are currently able to send only 20 bytes per packet but we want to send upto 128 bytes of data. 
 Can anyone help me to achieve this?

Einar Thorsrud · Accepted Answer

Hi, 
 You typically want to both enable larger GATT packets and larger GAP packets using data length extension. I suggest you take a look at the Nordic UART Service Client and UART/Serial Port Emulation over BLE from nRF5 SDK 17.1.0 for examples that do this on the central and peripheral respectively. 
 Note particularily the value of NRF_SDH_BLE_GATT_MAX_MTU_SIZE (247) and NRF_SDH_BLE_GAP_DATA_LENGTH (251) in sdk_config.h for both examples, and that in the central example, nrf_ble_gatt_att_mtu_central_set() is called.

How to increase the packet size for sd_ble_gattc_write

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