Mass storage with nRF51?

[Sensors]

I have a project that requires a bluetooth central to be used to gather data from a HRM service, which shouldn't be too much of an issue. However, it also has to store this, and other local sensor data to some sort of storage device (perhaps microSD or Flash memory).

I want to be able to access this data from a PC or other device, but I'm not sure if the nRF51 or nRF52 has the ability to support a file system and act as a USB mass storage device. Would I need to use an additional part to make this possible? If so, what options do I have?

Thanks

[RK]

you have two SPIs on the chip, and it's not necessarily SPI you'll need - depends on the chip you use to support the MSD. You could even possibly hook it up so they are independent users of the same memory .. but I think I wouldn't do that.

I just did some googling - there are fewer USB MSD chips than I would have thought, well that I've found so far at least. There's lots of USB CDC serial ones, but I guess that's because all they have to do is be USB one side and UART the other and you can interface them with anything, USB MSD really needs code on the host side.

Atmel has the SAMD11, cheap, has USB, they have an MSD example, it's also crystal-less which is rather handy. If you haven't done any USB stuff before however .. you have a lot to learn I'm afraid. Now you've made me curious enough to put it on my project list, couple of weeks of fun there.

[RK]

.. there has to be more out there however .. you can get such ridiculously cheap USB sticks, they must have a really simple USB MSD controller in them, same for the adapters you plug SD cards into, they're flipping tiny, 5v powered and talk USB and SD, figure out what chip they use and you may have a solution.

[Wojtek]

Just about SAMD11 - i used that chip for USB CDC serial - atmel has quite good libraries but with a bit large overhead. samd11 has quite small memory (ram and rom) but should be enough for mass storage (with external memory ofc). It was quite easy for me to start with it, and i am still a novice :) also Its QFN package is really small :)

[Sensors]

So do we think the best approach here might be to use a separate microcontroller to deal with the USB comms, flash/file system, and have the nRF51 act as the system to gather the data from bluetooth and other sensors?

If that's all the nRF51 is doing though then maybe it's overpowered for the task when I could potentially just get away with some sort of BLE central IC that requires no custom firmware? Does Nordic make a 'dumb' BLE central IC?

[Wojtek]

Think what that ic has to do. Is it only scanning or also connecting? how would you send the data to "master" uc? Is the service standard or custom? I think it is easier just to stay with nRF51 instead of using other ic.