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WiFi Add-on for Rapberry Pi Zero: Zero Pants

2016-05-16 21:19 - Making

I recently became the proud owner of a Raspberry Pi Zero. An amazing little gadget for its $5 price point! But as a result the features are a bit spare. When I found this RPi WiFi project on Hackaday I was hooked, I needed to have one. But it's not available, yet.

The original project is more ambitious than my adaptation of it. I only put the ESP module and a breakout for (power and) serial data. A stacking header mates with male header pins attached to the Zero, and voila! The original seemed to be called "WiFi Pants", with my simpler version intended to work with the Pi Zero, I chose to call mine "Zero Pants".

There's just one caveat: it doesn't start at boot. I'm pretty confident this is because I'm using the ESP-12-E module, which is set up with embedded flash and program to run. So I have to do the GPIO twiddle in step 10 of the instructions. But that causes a kernel panic. Actually what I need to do, so I have for now as a script file, is:

#!/bin/sh
rmmod esp8089
echo 0 > /sys/class/gpio/export
echo low > /sys/class/gpio/gpio0/direction
echo in > /sys/class/gpio/gpio0/direction

Remove the kernel module first, then toggle the GPIO pin to cause the ESP to restart. The module automatically reloads itself, and if you have a valid wpa_supplicant.conf set up, it connects in just a few moments.

Plus I needed to patch the esp8089 module to get it to compile for the recent kernel I got by following the instructions. (As mentioned in the comments.) But hey, it was a nice fun small project!

I ended up not installing either of the LEDs in this, the second module that I assembled. I got something wrong so the power LED was unnecessarily bright, and the "init" LED did indeed blink correctly to let me know the GPIO was twiddled. But it's normally high, so stays on the whole time, and also terribly dim, because it's being powered through the (I assume?) processor's internal pullup resistor. So no need to keep that!