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 to use a separate MCU if you want to deal with USB, you just can't do it with the nRF series. I'm a pretty good programmer but even I would balk at trying to bitbang USB :).

Don't think Nordic makes a dumb central IC, they have the 8001 series but those are peripheral only, they have the nRF24L series but those are generic 2.4GHz and don't have a BLE stack (I think) and they are 8051 processor, they do have USB however (but probably no MSD driver).

There are other standalone BLE chips, Atmel again, Microchip again, which you just talk to over serial, however I don't know as you save much money using one, even when you have the full BOM to support the nRF chip. I'd move to the nRF52 myself, less components needed on the matching network (ie just 2).

Or don't use mass storage, get the data off another way, .. serial?

[Sensors]

The service would be the standard HRM service. All the central would have to do is receive that data and pass it on.

Potentially I could get the data by other means, but it needs to be relatively user friendly without being too compliated :/

I'll have a look at the other standalone BLE chips vs the nRF52. BOM cost is obviously a significant factor so I need to weight that up against assembly/programming complexity.

No way in hell am I gonna be bit-banging USB though!

[RK]

well the cheapest USB MSD chip I can find is some OTI device which you can get for $1.50 a pop but interfaces directly to NAND memory and still needs a crystal. Octopart tells me I can get ATSAMD11 for about $2.20 a pop, doesn't need a crystal and you can program it to do what you want. So if I was doing this project, I'd start there myself. With that chip you can even get cute and implement a serial interface for streaming, testing or DFU .. or anything else you like.

i think I have a D11 eval board somewhere, might even have come with the BTLC1000 module (which is Atmel's BLE chip) which I've still not got around to actually using.