the Salt Mines gyro button

.gitignore

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+gyro

README.md

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+## Gryo Button
+
+When you press the button on an Amazon Dash, we increment the Salt
+Mines gyro counter.  See the current count [on the
+dashboard](http://dashboard.saltmines.us/south).
+
+Inspired by [this article by Ted
+Benson](https://medium.com/@edwardbenson/how-i-hacked-amazon-s-5-wifi-button-to-track-baby-data-794214b0bdd8).
+
+## Development and deployment
+
+This runs on the Raspberry Pi in the office.  I develop it on my Mac
+and cross compile it for linux/arm.  You will need Go with the
+linux/arm toolchain.  If you're on a Mac, this is easy:
+
+    $ brew install --with-cc-common go
+
+Once that's done:
+
+    $ GOOS=linux GOARCH=arm go build
+
+Then scp the `gyro` binary to `[email protected]` and run it:
+
+    $ sudo ./gyro wlan0

gyro.go

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+package main
+
+import (
+	"log"
+	"net"
+	"net/http"
+	"net/url"
+	"os"
+
+	"github.com/mdlayher/arp"
+)
+
+const gyroURL = "http://saltmines.us/gyroup.php"
+const name = "Some button pusher"
+
+func main() {
+	if len(os.Args) < 2 {
+		log.Fatal("Usage: arp <iface>")
+	}
+
+	iface, err := net.InterfaceByName(os.Args[1])
+	if err != nil {
+		log.Fatal("InterfaceByName: ", err)
+	}
+
+	c, err := arp.NewClient(iface)
+	if err != nil {
+		log.Fatal("arp.NewClient: ", err)
+	}
+
+	for {
+		p, _, err := c.Read()
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		if p.Operation == arp.OperationRequest && p.SenderIP.Equal(net.IPv4zero) {
+			resp, err := http.PostForm(gyroURL, url.Values{"user_name": {name}})
+			if err != nil {
+				log.Printf("Error updating count: %s", err)
+			}
+			resp.Body.Close()
+		}
+	}
+}