Please suggest me the best ways to transfer data from nrf52840 to android

[Vishnu Pradeep]

Hi, 

We have an embedded flash of 4Gbit which stores sensor data. The data needs to be transferred to a Smartphone. Now we are using USB cdc acm for transferring data with an OTG cable and USB cable. But it is taking from 30 minutes to 1.5 hours depending on the smartphone. 

I found this https://github.com/NordicPlayground/nrf52-ble-image-transfer-demo which says it is possible to send data over BLE? BUt I need to know how fast this can be done? the maximum data rate which is possible. The data transfer also depends on the speed at which data is read from flash.

Data is stored as files. Each file contains one hour sensor data.  TC58CYG2S0HxAIx is the flash we are using and 32 MHz SPI is used for interfacing. 

Below is the sequence for sending the data from device to application.

After successful USB connection (authenitcating Username and all) with smartphone, device starts sending data.

read 4KB data from flash > sends 4KB via USB > waits for acknowledgment > Repeats until all the files are transferred.

I would like to know the options to increase the transfer speed. Is BLE transfer rate has speed advantage over USBcdc acm?

Regards,

Vishnu Pradeep

[Bulhar]

Hi, in general, BLE will be much slower than USB. Better way could be bluetooth classic, but it is still slower than USB. The BLE is targeting to applications where small pieces of data are transferer. Theoretical max speed is 2 Mbps (BLE 5.0). I guess USB is the fastest way for connection with smart phone. If you  require wireless interconnection try think about wifi. 

[Vishnu Pradeep]

But I am getting less than 100KBps for the USB now. So if both USB and BLE is giving almost similar speed I thought of switching to BLE to save some BOM cost