Mass storage with nRF51?

RE: Mass storage with nRF51?

RK — Wed, 22 Jun 2016 12:40:39 GMT

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.

RE: Mass storage with nRF51?

Sensors — Wed, 22 Jun 2016 10:56:26 GMT

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!

RE: Mass storage with nRF51?

RK — Wed, 22 Jun 2016 10:56:25 GMT

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?

RE: Mass storage with nRF51?

Wojtek — Wed, 22 Jun 2016 10:37:46 GMT

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.

RE: Mass storage with nRF51?

Sensors — Wed, 22 Jun 2016 10:35:07 GMT

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?

RE: Mass storage with nRF51?

Wojtek — Wed, 22 Jun 2016 09:43:57 GMT

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 :)

RE: Mass storage with nRF51?

RK — Wed, 22 Jun 2016 09:33:00 GMT

.. 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.

RE: Mass storage with nRF51?

RK — Wed, 22 Jun 2016 09:31:18 GMT

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.

RE: Mass storage with nRF51?

Sensors — Wed, 22 Jun 2016 09:24:15 GMT

RK, will that not interfere or clash with the SPI coming from the nRF51? I've not had to do anything like this before, so I'm not sure about the best way to go about it. I'm also not sure what to search for in terms of part description/name?

Wojtek, unfortunately it has to be a cost effective, scalable design so unfortunately cramming and Edison or rPi in a box won't work :(

RE: Mass storage with nRF51?

Wojtek — Wed, 22 Jun 2016 09:06:46 GMT

Do you have power source there? Maybe you could use some module like ex. new raspberry pi, or intel edison, and their in-built BLE? you could access the data by WiFi or something. But it would be much more expensive in mass production.

RE: Mass storage with nRF51?

RK — Wed, 22 Jun 2016 09:05:36 GMT

In that case you don't need an SD card and all the expense of the holder if you're not going to take it out again. Just use some cheap SPI addressed soldered in flash memory, cheaper, easier.

If you must have USB then buy a USB capable interface chip, I'm sure FTDI does them, Atmel does them, there's bound to be lots of others, probably come ready-configured to look like serial ports or MSDs and you just need to feed them, probably via SPI again.

RE: Mass storage with nRF51?

Sensors — Wed, 22 Jun 2016 09:01:49 GMT

It's not a viable option to take the SD card out, it must be a self-contained unit. It's awkward, but necessary in this case.

Re-transmitting the data via BLE is potentially an option, but 1GB of data would take over two hours at BLE's 1Mbps.

RE: Mass storage with nRF51?

RK — Wed, 22 Jun 2016 08:59:25 GMT

You take the micro SD card out and plug it into a USB adaptor and put it in the computer you want to download the data onto. That's how you access it over USB.

I believe FreeRTOS also has a free FAT filesystem which you can use without the actual RTOS, so you just need to write the SPI driver for the MicroSD card which is tedious but not very hard.

Alternatively since you have bluetooth how about just retransmitting the data over bluetooth to the host computer.

RE: Mass storage with nRF51?

Wojtek — Wed, 22 Jun 2016 08:57:18 GMT

card reader. nrf51 is not capable to do usb-emulation.

RE: Mass storage with nRF51?

Sensors — Wed, 22 Jun 2016 08:54:26 GMT

Yeah, I thought I may be able to do that through SPI. I hoped maybe Nordic supported FatFS or something similar, but I may need to port it.

However, how would I then access this data via USB?

RE: Mass storage with nRF51?

Wojtek — Wed, 22 Jun 2016 08:51:22 GMT

Ok, i think the easiest way is to use SD-card. You can write to it using SPI (probably some level-shifting will be needed). Maybe you could implement FAT32 filesystem somehow. If not, you can write RAW data on that card, but you will have to use some special software to read from it on the PC.

RE: Mass storage with nRF51?

Sensors — Wed, 22 Jun 2016 08:46:25 GMT

Potentially between 0.5-1GB...

RE: Mass storage with nRF51?

Wojtek — Wed, 22 Jun 2016 08:43:54 GMT

how big storage you need?