nRF Connect Device Manager <-> implement SMP-Server on nRF52840 running SDK 16

[Tommy F Kristensen]

Hi 

I have a board nRF52840 configured with some QSPI with filesystem configured

I would like to manage the file system from an app and I saw that - nRF Connect Device Manager, can do this but it requires an SMP server that looks like it is only implemented on Zephyr

List files, upload and download files, from the device to the smartphone

Is it possible to port or are there already implemented an SMP- server on the native code running on the nRF 52840 with SDK 16

Are there any other examples on file transfer ?

Best Regards

Tommy F Kristensen

[Jørgen Holmefjord]

Hi,

I'm not aware of any implementation of SMP server for nRF5 SDK.

As an alternative, you may have a look at the Object Transfer Service Server Application. You will need to implement some logic around file listing, reading and writing, but I think this approach may be simpler than porting the full SMP server implementation.

Best regards,
Jørgen

[Jørgen Holmefjord]

Hi Tommy,

The image transfer demo is also a good alternative to start out with. This example uses a custom GATT service similar to Nordic UART Service, compared to OTS which sends the data over a separate L2CAP channel. L2CAP may have slightly higher throughput than GATT (which works on top of L2CAP), but the maximum throughput gain may not be worth the added complexity (see for instance GATT vs Raw LL data in table 2 in Bluetooth Low Energy data throughput).

GATT should be well supported in both iOS and Android, for both older and newer phone models. However, note that the supported features in different phones may greatly affect the achievable throughput (support for 2Mbit PHY, increased ATT MTU size, Data Length Extension (DLE), etc), see examples in this table. We have applications available for both Android and iOS

Best regards,
Jørgen

[Tommy F Kristensen]

Hi Jørgen

Thanks for your answer, I will try to use the Image transfer demo even that it is slightly more complex. 

It looks like it should be a good stating point to send and receive files from/to the BLE device,  

as it includes some examples on how to transfer a files and send commands to the device.

Functions like, ble_its_send_file(), that would automatically send the file in chunks to the Android app

I like this example as is has code both for the nRF52840 chip and the Android.

Is there made sample code for IOS(Iphone) ?

 Best Regards

Tommy F Kristensen

[Jørgen Holmefjord]

Tommy F Kristensen said:

Is there made sample code for IOS(Iphone) ?

Yes, I see that it is not linked on the firmware GitHub page, but I did post a link in my previous reply: https://github.com/NordicPlayground/iOS-Image-Transfer-Demo

[Tommy F Kristensen]

Hi Jørgen

Thanks for fast response, that will be great to have a reference for implementing the file transfer application on IOS.

I have had success porting to my solution, but  changing the NRF_SDH_BLE_GATT_MAX_MTU_SIZE and NRF_SDH_BLE_GAP_DATA_LENGTH, takes up a lot of RAM for the softdevice.

Are there made any experiments/calculations on what parameters that give the largest improvements compared to the RAM usage.

Currently I have updated the parameters to following:

NRF_SDH_BLE_GATT_MAX_MTU_SIZE 125

NRF_SDH_BLE_GATT_MAX_MTU_SIZE 112

NRF_SDH_BLE_GAP_EVENT_LENGTH 12

I have seen transferrates on about  29-59kbps on 13kb jpeg file

Im using a Samsung S8, what can I expect ?

Best Regards

Tommy F Kristensen

[Jørgen Holmefjord]

Hi,

Unfortunately, I'm not aware of any such calculations. I would recommend you to use the highest settings that you can fit with your available RAM space.

According to the table in the Android application repository, ~1200kbps should be achievable with Samsung Galaxy S8, but this would probably require 2Mbit PHY, 247 byte ATT MTU, 251 byte DLE, and appropriate connection event length depending on your connection interval.

Best regards,
Jørgen