examples: use hid-keyboard example to show how to to override default USB VID, PID, manufacturer name, and product name

Signed-off-by: deadprogram <ron@hybridgroup.com>

src/examples/hid-keyboard/main.go

@@ -1,11 +1,22 @@
+// to override the USB Manufacturer or Product names:
+//
+// tinygo flash -target circuitplay-express -ldflags="-X main.usbManufacturer='TinyGopher Labs' -X main.usbProduct='GopherKeyboard'" examples/hid-keyboard
+//
+// you can also override the VID/PID. however, only set this if you know what you are doing,
+// since changing it can make it difficult to reflash some devices.
 package main
 
 import (
 	"machine"
+	"machine/usb"
 	"machine/usb/hid/keyboard"
+	"strconv"
 	"time"
 )
 
+var usbVID, usbPID string
+var usbManufacturer, usbProduct string
+
 func main() {
 	button := machine.BUTTON
 	button.Configure(machine.PinConfig{Mode: machine.PinInputPullup})
@@ -19,3 +30,23 @@ func main() {
 		}
 	}
 }
+
+func init() {
+	if usbVID != "" {
+		vid, _ := strconv.ParseUint(usbVID, 0, 16)
+		usb.VendorID = uint16(vid)
+	}
+
+	if usbPID != "" {
+		pid, _ := strconv.ParseUint(usbPID, 0, 16)
+		usb.ProductID = uint16(pid)
+	}
+
+	if usbManufacturer != "" {
+		usb.Manufacturer = usbManufacturer
+	}
+
+	if usbProduct != "" {
+		usb.Product = usbProduct
+	}
+}