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Maximum number of bytes sent in one frame BLE PSoC 4 | Cypress Semiconductor

Maximum number of bytes sent in one frame BLE PSoC 4

Summary: 2 Replies, Latest post by madhusudan.sangam_1571016 on 06 Feb 2016 10:10 AM PST
Verified Answers: 1
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cyguevara_1509311's picture
18 posts

Hi everyone,


I'm trying to send 26 bytes in one frame via BLE, I first tried using 20 bytes and it works good, but if i try to send 21 bytes, i don'r receive any data.


Do you know why is ths happening?



mady's picture
Cypress Employee
964 posts


You need to increase the MTU Size. It is by default 23 bytes. You have to increase it to a higher value in both Central and Peripheral.

Also, the central and peripherals need to negotiate the actual MTU Size after the connection is established.

(i) Set the MTU Size in the component settings of Client and Server to a greater value.

(ii) The client should initiate the negotiation by calling CyBle_GattcExchangeMtuReq.

(iii) This invokes CYBLE_EVT_GATTS_XCNHG_MTU_REQ event on server.

​(iv) The server should respond with the MTU Size using CyBle_GattsExchangeMtuRsp API

(v) This would result in CYBLE_EVT_GATTC_XCHNG_MTU_RSP event the client.

Refer to the BLE Component datasheet for details.


- Madhu Sudhan


Please check the 



Hi madhusudan,

Thanks a lot for the reply, i will check the same

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