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I have two Model A+ Pis and a Model B+, as well as a couple of USB A-to-A Male cables. I want to be able to have the A+es able to communicate over serial to the B+. The reason I'm doing this is because I also have some camera modules, and I want the A+es to take pictures, extract some information, and send a summary over the cable for further processing.

Is there any way to switch the A+es into USB Device Mode so they'll be detected as a serial peripheral (like an Arduino would be) when I plug them into the B+ using the A-to-A cables?

Will
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Ryan Kennedy
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3 Answers3

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Did you consider connecting the devices directly with simple dupont wires between their UARTs (GPIO Pins 14 and 15) ?

The UART pins are also known as Pins 8 and 10

If you are very adventurous , you can install pppd and even use IP-based tools over the serial link (SSH , FTP etc.) -> See here

flakeshake
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If you consire Raspberry PI Zero an option, there is tutorial at https://learn.adafruit.com/turning-your-raspberry-pi-zero-into-a-usb-gadget/serial-gadget. Raspberry PI Zero has proper OTG support on both USB ports.

On the software level you'd need kernel with "gadget" drivers compiled as modules, g_serial module loaded and software to communicate over that serial port.

There are high chances that OTG support will land in 4.4 kernel for Raspberry PI, see https://github.com/raspberrypi/linux/pull/1239

myroslav
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I believe the answer is definitely not for the B(+) and only theoretically for the A(+). See this answer for a concise explanation regarding the former (it comes down to the fact the ethernet jack shares the USB bus).

This Q&A has some more discussion, including the potential of the micro USB power jack (no luck).

The problem with the A models is that there is no system software to support this, or at least, none that's been demonstrated.

Community
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goldilocks
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