nRF52832 BLE improve transfer file with UART service

RE: nRF52832 BLE improve transfer file with UART service

PederOlav — Fri, 07 Jun 2019 11:48:13 GMT

Thank you very much for good and understandable answers :-)

Best regards

Peder Olav

RE: nRF52832 BLE improve transfer file with UART service

bjorn-spockeli — Fri, 07 Jun 2019 11:16:51 GMT

HI Peder Olav,

[quote user=""]

1) What is the reason why our device (slave) respond with an Empty PDU first, after received a write request?

[/quote]

If the slave does not have any data to send at the scheduled connection interval it will respond with an empty PDU. Both master and SLave will send empty PDUs if there are no data to be sent in order to maintain link synchronization, i.e. make sure that the timers that keep track of when to turn the radio on in TX/RX mode does not drift apart.

[quote user=""]2) We have now set wr_auth=1. If we set this to 0, will we get higher transfer rate? And if so what kind of pitfalls can there be?[/quote]

Yes, Write Commands and Write Requests will require the application to authorize any values that is written to which reduce the throughput., please see the GATT Server Message Sequence Charts as well as the Bluetooth Low Energy data throughput section of the S132 SoftDevice Specification. Read/Write Authorization can be useful in some cases, but if throughput is the most important factor, then you should go for Write Commands without authorization.

[quote user=""]3) Should we increase the MTU size from 23? Is this a good choice? If increasing the MTU size will this mean higher current consumption?[/quote]

Increasing the ATT MTU size will result in less overhead as you can fit more ATT data within one BLE packet. You reduce the overhead by not sending the ATT header, which in turn is more effcient use of the radio.

[quote user=""]4) Is it possible within the same software, since our device can both act like Central and Pheripheral, to have two different MTU sizes?
E.g when Master runs with 23 bytes and Slave with 128 bytes.[/quote]

As of S132 v4.0.x the MTU length can be individually configured per link. So yes.

[quote user=""][/quote]

4) Are there other ways we can improve the transfer with NUS?

5) Should we look into another service, e.g. Object Transfer Service?

I recommend that you take a look at the Experimental: ATT_MTU Throughput Example in our SDK.

Best regards

Bjørn

RE: nRF52832 BLE improve transfer file with UART service

awneil — Thu, 06 Jun 2019 09:44:19 GMT

[quote userid="79337" url="~/f/nordic-q-a/48212/nrf52832-ble-improve-transfer-file-with-uart-service/191242"] I guess the phone will use perhaps the min.interval[/quote]

Unfortunately not.

😞

As I said, most phones will not allow that low.

RE: nRF52832 BLE improve transfer file with UART service

PederOlav — Thu, 06 Jun 2019 07:29:23 GMT

You are right. I checked our software and min. interval is 7.5 ms and max. 50 ms for our peripheral setup. Latency is 0.So I guess the phone will use perhaps the min.interval

RE: nRF52832 BLE improve transfer file with UART service

awneil — Wed, 05 Jun 2019 16:34:42 GMT

[quote userid="79337" url="~/f/nordic-q-a/48212/nrf52832-ble-improve-transfer-file-with-uart-service"]connection interval 50ms[/quote]

That's very slow!

The spec minimum limit is 7.5ms, although most phones will not allow that low.