NRF maximum gatt mtu size

RE: NRF maximum gatt mtu size

Petter Myhre — Thu, 23 Nov 2017 13:59:56 GMT

You can have a look at the ble_app_att_mtu_throughput example, see if you see any differences. This configures for maximum throughput. What event length are you using? If the connection interval is 400 ms, the event length should also be 400 ms. 424.6 kbps is the maximum measured throughput in 1Mbps with simultaneous send Notification and receive Write command. Only sending notifications one way you can achieve 771.1 kbps.

It also depends what you are connecting to, what kind of central device is it? You will typically only achieve the numbers above when you have our devices in both ends of the link.

RE: NRF maximum gatt mtu size

pranavsk1994 — Wed, 22 Nov 2017 18:45:31 GMT

I am using nrf 13.0.0 SDK, with nrf52840 chip, and S140 softdevice. I didn't understand how to use the DEBUG option. But I solved the error I was not initializing the MAX size in ble stack. Now I am able to set att mtu to 247 bytes. But the throughput is coming out around 106 Kbps. But in the following link its mentioned you can get a throughput of 424 kbps for GATT size of 247, max conn interval time of 400ms. infocenter.nordicsemi.com/index.jsp

I don't understand if I am missing something here

RE: NRF maximum gatt mtu size

Petter Myhre — Wed, 22 Nov 2017 18:19:27 GMT

Did you try my suggestion?

RE: NRF maximum gatt mtu size

pranavsk1994 — Wed, 22 Nov 2017 17:13:36 GMT

So the data I recieve over SPI from peripheral device is sampled at really fast rate. I am not sending only 5 bytes over ble. I am pushing data recieved over SPI to ble queue till I get an err_code message of NRF_ERROR RESOURCES. I want tp increase the ATT_MTU size which is currentky set to 158 in my config file. But if I increase it to 247 which is maximum as mentioned in documents the code doesn't seem to work. It doesn't even advertise.

RE: NRF maximum gatt mtu size

Petter Myhre — Wed, 22 Nov 2017 09:58:26 GMT

Do you really need a bigger ATT MTU? If you are sending 5 bytes at the time?

Anyways, which SDK and SoftDevice version are you using? Which example? Sounds like you are getting an error code somewhere and the chip resets. Please try to turn off optimizations, define DEBUG, and set a breakpoint in app_error_handler(). If you hit the breakpoint, extract the error code, line number and file name.