unor4wifi: add WiFi driver for the Arduino UNO R4 WiFi

examples/net/ntpclient/main.go

@@ -3,7 +3,7 @@
 // It creates a UDP connection to request the current time and parse the
 // response from a NTP server.  The system time is set to NTP time.
 
-//go:build ninafw || wioterminal || challenger_rp2040 || comboat_fw
+//go:build ninafw || wioterminal || challenger_rp2040 || comboat_fw || arduino_uno_r4_wifi
 
 package main
 

examples/net/socket/main.go

@@ -4,7 +4,7 @@
 //
 // nc -lk 8080
 
-//go:build ninafw || wioterminal || challenger_rp2040 || comboat_fw
+//go:build ninafw || wioterminal || challenger_rp2040 || comboat_fw || arduino_uno_r4_wifi
 
 package main
 

examples/net/tcpclient/main.go

@@ -5,7 +5,7 @@
 //
 // nc -lk 8080
 
-//go:build ninafw || wioterminal || challenger_rp2040 || comboat_fw
+//go:build ninafw || wioterminal || challenger_rp2040 || comboat_fw || arduino_uno_r4_wifi
 
 package main
 

examples/net/tcpecho/main.go

@@ -7,7 +7,7 @@
 //
 // $ nc 10.0.0.2 8080 <file >copy ; cmp file copy
 
-//go:build ninafw || wioterminal
+//go:build ninafw || wioterminal || arduino_uno_r4_wifi
 
 package main
 

examples/net/tlsclient/main.go

@@ -5,7 +5,7 @@
 //
 // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security
 
-//go:build ninafw || wioterminal || comboat_fw
+//go:build ninafw || wioterminal || comboat_fw || arduino_uno_r4_wifi
 
 package main
 

examples/net/webclient/main.go

@@ -17,7 +17,7 @@
 // }
 // ---------------------------------------------------------------------------
 
-//go:build ninafw || wioterminal || comboat_fw
+//go:build ninafw || wioterminal || comboat_fw || arduino_uno_r4_wifi
 
 package main
 

netlink/probe/unor4wifi.go

@@ -0,0 +1,27 @@
+//go:build arduino_uno_r4_wifi
+
+package probe
+
+import (
+	"machine"
+
+	"tinygo.org/x/drivers/netdev"
+	"tinygo.org/x/drivers/netlink"
+	"tinygo.org/x/drivers/unor4wifi"
+)
+
+func Probe() (netlink.Netlinker, netdev.Netdever) {
+
+	cfg := unor4wifi.Config{
+		// UART3 is the SCI1 link to the ESP32-S3 AT interface.
+		Uart:     machine.UART3,
+		Tx:       machine.UART3_TX_PIN,
+		Rx:       machine.UART3_RX_PIN,
+		BaudRate: 115200,
+	}
+
+	dev := unor4wifi.New(&cfg)
+	netdev.UseNetdev(dev)
+
+	return dev, dev
+}

smoketest.sh

@@ -194,3 +194,6 @@ tinygo build -size short -o ./build/test.hex -target=wioterminal -stack-size 8kb
 # network examples (comboat)
 tinygo build -size short -o ./build/test.hex -target=elecrow-rp2040 -stack-size 8kb ./examples/net/tlsclient/
 tinygo build -size short -o ./build/test.hex -target=elecrow-rp2350 -stack-size 8kb ./examples/net/ntpclient/
+# network examples (unor4wifi)
+tinygo build -size short -o ./build/test.hex -target=arduino-uno-r4-wifi -stack-size 2kb ./examples/net/tcpclient/
+tinygo build -size short -o ./build/test.hex -target=arduino-uno-r4-wifi -stack-size 2kb ./examples/net/ntpclient/

unor4wifi/README.md

@@ -0,0 +1,75 @@
+# unor4wifi
+
+WiFi network driver for the Arduino UNO R4 WiFi.
+
+The board has a Renesas RA4M1 main MCU and an ESP32-S3 WiFi module. The
+ESP32-S3 runs the Arduino [uno-r4-wifi-usb-bridge][bridge] firmware. The
+RA4M1 talks to it over UART (SCI1, `machine.UART3`) with an AT style
+protocol. This driver speaks that protocol and implements the
+[netlink](../netlink) and [netdev](../netdev) interfaces, so the standard
+`net` package works.
+
+Keep the stock bridge firmware on the ESP32-S3. Do not flash the ESP32-S3.
+
+## Supported
+
+- WiFi station mode (`ConnectModeSTA`) with WPA2 or open networks
+- WiFi access point mode (`ConnectModeAP`)
+- TCP client and TCP server
+- UDP
+- DNS lookup
+
+## Not supported
+
+- TLS offload in the ESP32-S3. Use the Go `crypto/tls` package instead.
+- Socket options (`SetSockOpt` returns `netdev.ErrNotSupported`).
+- BLE. The bridge has HCI pass-through commands, but this driver does not
+  use them.
+
+## Usage
+
+```go
+import (
+	"tinygo.org/x/drivers/netlink"
+	"tinygo.org/x/drivers/netlink/probe"
+)
+
+link, _ := probe.Probe()
+err := link.NetConnect(&netlink.ConnectParams{
+	Ssid:       "my-ssid",
+	Passphrase: "my-passphrase",
+})
+```
+
+Then use `net.Dial`, `net.Listen` and so on.
+
+The RA4M1 has 256 KB of flash. The `net/http` package does not fit.
+Use the `net` package directly, or a small client such as the `ntpclient`
+or `tcpclient` examples.
+
+Build with `-target=arduino-uno-r4-wifi -stack-size 2kb`. The RA4M1 has
+32 KB of RAM and each goroutine gets a stack of the given size, so a larger
+stack size leaves too little heap. The network examples that fit in flash
+(`socket`, `tcpclient`, `tcpecho`, `ntpclient`, `tlsclient`, `webclient`)
+carry the `arduino_uno_r4_wifi` build tag.
+
+Do not use `io.Copy` with a `net.TCPConn` on this board. It allocates a
+32 KB buffer. Use a `Read`/`Write` loop with a small buffer instead.
+
+## Protocol
+
+Commands and response formats are defined in the bridge firmware:
+
+- [commands.h][commands]
+- [cmds_wifi_netif.h][netif] (TCP client and server)
+- [cmds_wifi_udp.h][udp]
+
+Text responses look like `+CMD:<data>\r\nOK\r\n`. Binary responses from
+`+CLIENTRECEIVE` and `+UDPREAD` look like `+CMD:<len>|<len bytes>OK\r\n`.
+Payload for `+CLIENTSEND` and `+UDPWRITE` follows the command line as raw
+bytes.
+
+[bridge]: https://github.com/arduino/uno-r4-wifi-usb-bridge
+[commands]: https://github.com/arduino/uno-r4-wifi-usb-bridge/blob/main/UNOR4USBBridge/commands.h
+[netif]: https://github.com/arduino/uno-r4-wifi-usb-bridge/blob/main/UNOR4USBBridge/cmds_wifi_netif.h
+[udp]: https://github.com/arduino/uno-r4-wifi-usb-bridge/blob/main/UNOR4USBBridge/cmds_wifi_udp.h

unor4wifi/debug.go

@@ -0,0 +1,16 @@
+package unor4wifi
+
+type debug uint8
+
+const (
+	debugBasic  debug = 1 << iota // show fw version, mac addr, etc
+	debugNetdev                   // show netdev entry points
+	debugCmd                      // show AT cmds
+
+	debugOff = 0
+	debugAll = debugBasic | debugNetdev | debugCmd
+)
+
+func debugging(want debug) bool {
+	return (_debug & want) != 0
+}