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Maximum value for ATT_MTU

Hi

When initialising BLE in the softdevice, the following value is used as part of enable_params:-

 * @brief BLE GATT initialization parameters.
 */
typedef struct
{
  uint16_t  att_mtu;          /**< Maximum size of ATT packet the SoftDevice can send or receive.
                                   If it is 0 then @ref GATT_MTU_SIZE_DEFAULT will be used.
                                   Otherwise @ref GATT_MTU_SIZE_DEFAULT is the minimum value.
                                   @mscs
                                   @mmsc{@ref BLE_GATTC_MTU_EXCHANGE}
                                   @mmsc{@ref BLE_GATTS_MTU_EXCHANGE}
                                   @endmscs
                              */
} ble_gatt_enable_params_t;

I know that the minimum (and default) size for ATT_MTU is 23 bytes as defined in ble_gatt.h:-

/** @brief Default MTU size, in bytes. */
#define GATT_MTU_SIZE_DEFAULT 23

However, there is no specification for the maximum size, so what is the maximum size that can be used?

I am using softdevice s132 v3.0.0 on nRF52.

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  • Please try to raise new questions as separate topics. This increases visibility and increases the chance of you receiving the best response. It also makes it much easier for future visitors to find the answer to their own, similar question.

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