I'm looking for a way to use raspberry as a slave usb device.

I noticed that the usb port of the model B/B+/2 is connected to a hub chip (as is the ethernet plug), and then to the processor, so the hardware prevent me from using it as slave, as discussed in this Q&A.

So, i start looking for an external USB chip that i could connect to the rasperry (UART / Serial most probably), and which i can entirely control : Computer <= USB => Chip <= Serial => Rpi

Every chip I found (here for example : http://www.ftdichip.com/) handle the USB protocol itself what I'm looking for, as I really need to do the usb stuff myself.

Do you know a chip that "convert" serial to male USB without handling USB protocol itself, or a USB chip i could program entirely (no protocol handling again, so no firmware ?)


If you can get Synopsys to give you the reference manual of the USB block used in BCM283[56], you can rewrite the USB driver to support such operation. The Model A/A+ have its USB port exported directly from the Broadcom chip so if you get this to work you can test it without hacking the hardware.

Or you will need some sort of bridging mechanism like USB to Serial or USB slave to SPI slave adapter chips. The former is simple to implement and if you need more UART you can always use an NXP SC16IS752 I2C UART chip (kernel driver included in latest Raspbian kernel). The latter option would also require you to acquire manuals of the chip and write a kernel driver.

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