I am designing a board around the RBp Compute and would like to add WiFi connectivity to this device. However, I do plan on using USB 2.0 for its datarate (e.g. to send and receive images), so the ESP32 and other modules with UART comm are not viable options. Has anyone made a out of the box wifi module work with the Compute? And if yes, which ones? The Raspberry forums weren't really helpful. Thanks!
1 Answer
The compute module has USB signals on the SODIMM connector. USB_DP and USB_DM are the differential pair used for communication. You should be able to connect any USB device to these. Keep in mind that you will need to connect GND line as well, and in case of host-powered devices (the vast majority of WiFi adapters) you'll need to provide 5V to the adapter as well.
Note that USB 2.0 signals have a much higher frequency than e.g. GPIO pins (480 MHz vs. single-digit MHz), so you should make any wires / PCB trances carrying these signals as short as possible (and of equal length within ~5mm tolerance). Ideally, you should use a twisted pair with 90 Ω ± 10% total impedance. In particular, USB 2.0 will not work over stray jumper wires.
answered Dec 12, 2019 at 15:18
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My question was perhaps not formulated well, I am looking for viable modules.– Alex ErDec 12, 2019 at 15:48
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@AlexEr USB isn't exactly an exotic interface. I guess the official WiFi dongle is a decent choice. If you plan to solder a dongle directly (rather than fitting a USB connector), you may want to search for a cheaper variety which is often easier to disassemble and is less of a loss if you break it in the process. Dec 12, 2019 at 15:50
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Yes, but not all ICs/SoMs with USB interface seem to be equally well supported in the kernel. I'm looking for one that both supported, preferably used succesfully by someone, and over USB. The RT5370 based modules are a good start, for instance, but they are more for dev-purposes as far as I can tell, and not something to build in.– Alex ErDec 13, 2019 at 8:21