Mass storage emulation raspberry pi

If you use the Raspberry Pi Zero, it can emulate storage to another computer as if it were a USB stick. Is this what you are after?

Clem

Yes I believe so. Does it need additional boards? Or is it natively able to do this? After it receives a file I would like the pi to then print it.  So it would need to be booted into the OS while it is acting as a USB drive is that possible as well?

The CPU on the raspberry pi family has the ability to work as an "USB Device". The hardware on B, B+ and Pi3 however makes this impossible unless you probe signals internal to the board. The A, A+ and Zero however bring out the right signals on the USB connector.

There are however two problems with this approach. First there is the problem that this would use the ONLY usb peripheral on the chip. How are you going to connect to the printer? Through USB? No. Through Ethernet? Just need to add an USB-Ethernet adapter... Ah...shucks!

Secondly, there is no (open source) software that I know of that makes the pi behave as an USB device.

There now is open source software  (http://pi.gbaman.info/?p=699 )  that allows the pi to behave as an USB-device. As a mass-storage device everybody thinks that you would simple export the whole SD card. I don' think this is a good idea: both OSes (the one on the pi and the one on the "third party device") would cache disk-blocks of the storage. This would create big problems. So the best would be to have an image on the SD card that is exported as the USB-storage device. Then on the pi you would make some software to "peek" into the image and extract the report for printing.

Possibly you might be able to use an ESP8266 board to get connectivity on the pi with the USB port already taken?

My thought was to use the hardware UART on the pins as a USB if needed with a converter to 5V from 3.3V on Raspberry Pi pins. There are many to be found. As to programming, a CRON task could wake up and look in the appropriate directory and perform the operations needed to print the text.

Clem

I don't think that will work. The "third party device" expects to find an USB DRIVE, not an USB serial port.

Yes, in theory that solution would be possible. However the term "third party device" usually implies: "so we can't change its hardware or software".

For clarity, the previous post is to set up a USB for printing text. The OTG is used as a storage device.

C

Would I still be able to program the pi? the printer can use a ttl pin I was looking at this one:

https://www.adafruit.com/products/597?gclid=Cj0KEQjw5Ie8BRCJ9fHlr_bH24cBEiQAkoDQcWk-G6TSWUQmB1ZmDQsSc9VzhxNlfUwzMBKZW4Io…

Here is what you can do:

1. Buy Raspberry Pi Zero. Microcenter is good place if you are near one, Otherwise find one online.

2. Install software like https://gist.github.com/gbaman/50b6cca61dd1c3f88f41

3. Create a cron task to run python to read file(text based) and print to the thermal printer. It could run every few minutes. It would need to know the name(s) of the files being created. If it works, cleanup the files by deleting them.

Clem

Tutorial at https://learn.adafruit.com/turning-your-raspberry-pi-zero-into-a-usb-gadget/other-modules

Clem

Tutorial at https://learn.adafruit.com/turning-your-raspberry-pi-zero-into-a-usb-gadget/other-modules

Clem