Throughput ATT_MTU

We are using nrf52832 soc for our product development and using that we are trying to increase the throughput of our device using the information from the following forum:
Novel Bits throughput guide 
In this forum it states that the Maximum GATT MTU SIZE possible is 247 bytes in which 244 bytes of data is the actual payload size and if the data is greater than the limit, then it will split into multiple packets. So we tried to send more that 247 bytes of data just to check how the data split in multiple packet is working. We tried to sent 256 bytes of data and we were able to get 255 bytes of data without any splitting, which is more than 247 bytes. So we are wondering what is the Maximum GATT MTU SIZE possible in nrf52832 soc. 
We also looked into the throughput example provided by the nordic (ble_app_att_mtu) and in that MTU size is set to 247 and data length is set to 251 which is less that what we are able to send from nrf52832 to phone, is there any possible explanation for this?

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  • Hi

    First off, what SDK version are you using for development when transmitting up to 255 bytes? It's possible to advertise up to 255 bytes of data in later SDK versions using chained advertising. 255 bytes won't fit in AUX_ADV_IND (max 247), so the remaining data will be chained using AUX_CHAIN_IND. What data exactly goes here depends on advertising type and PHY. 

    We're also aiming to support chaining more than 255 bytes in advertising data in future nRFConnect SDK releases.

    Best regards,

    Simon

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  • Hi

    First off, what SDK version are you using for development when transmitting up to 255 bytes? It's possible to advertise up to 255 bytes of data in later SDK versions using chained advertising. 255 bytes won't fit in AUX_ADV_IND (max 247), so the remaining data will be chained using AUX_CHAIN_IND. What data exactly goes here depends on advertising type and PHY. 

    We're also aiming to support chaining more than 255 bytes in advertising data in future nRFConnect SDK releases.

    Best regards,

    Simon

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