diff --git a/README.md b/README.md index de437bcd..37851666 100644 --- a/README.md +++ b/README.md @@ -34,6 +34,36 @@ $ sudo apt-get install -y nodejs and then proceed as above :) If you connect to the raspberry pi over ssh, you might want to run the `saxi` server inside a tmux or screen session to have it stay running even if your ssh session disconnects. +#### Raspberry Pi Zero OTG + +![Pi Zero on an AxiDraw with a Y-shaped USB cable](docs/pi-zero.jpg) + +For the Pi Zero you can make a USB "OTG" cable out of two Micro-B cables and two 0.1" headers +to tap into the AxiDraw's 5V servo supply to power the Pi. This makes for a more compact +installation without the need for an additional wall-wart. + + +``` + +------ Center pin on servo rail + | +---- Ground pin on servo rail + | | + | | +Red -----+-|---- Red +Black -------+---- Black +White ------------ White +Green ------------ Green (sometimes Blue) +``` + +The Pi will also need to have the `dr_mode=host` parameter set in +`config.txt` to force host mode, since normal USB Micro cables do not +include the `ID` pin that would be used to signal that it is an OTG +connection. + +``` +echo dtoverly=dwc2,dr_mode=host | sudo tee -a /boot/config.txt +``` + + #### CORS If you want to connect to saxi from a web page that isn't served by saxi itself, you'll need to enable diff --git a/docs/pi-zero.jpg b/docs/pi-zero.jpg new file mode 100644 index 00000000..fea5733f Binary files /dev/null and b/docs/pi-zero.jpg differ