I get soft reset when MTU is bigger than 65

[Stefan]

Hello!

I am trying to increase the MTU size to get higher speeds. When I increase the MTU above 65 the application locks/software reset when doing transfer. Up to 65 it works. I have increased RAM memory for SoftDevice a lot. No difference. I check the return value of softdevice_enable(). Always zero. I have not enabled DLE.

65 sounds awfully close to 64, but it is still a bit strange value.

Any hints or tips would be appreciated

[Sigurd]

Hi,

What SDK version are you using? What example in the SDK are you testing this on?

In e.g. SDK 13 in the ble_app_uart example you set the ATT_MTU with the nrf_ble_gatt_att_mtu_periph_set() function:

void gatt_init(void)
{
    ret_code_t err_code;

    err_code = nrf_ble_gatt_init(&m_gatt, gatt_evt_handler);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_ble_gatt_att_mtu_periph_set(&m_gatt, 64);
    APP_ERROR_CHECK(err_code);
}