espat: implement TCPConn using AT command set

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

examples/espat/tcpclient/main.go

@@ -0,0 +1,83 @@
+// This is a sensor station that uses a ESP8266 or ESP32 running on the device UART1.
+// It creates a UDP connection you can use to get info to/from your computer via the microcontroller.
+//
+// In other words:
+// Your computer <--> UART0 <--> MCU <--> UART1 <--> ESP8266
+//
+package main
+
+import (
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/espat"
+)
+
+// access point info
+const ssid = "YOURSSID"
+const pass = "YOURPASS"
+
+// IP address of the server aka "hub". Replace with your own info.
+const serverIP = "0.0.0.0"
+
+// change these to connect to a different UART or pins for the ESP8266/ESP32
+var (
+	uart = machine.UART1
+	tx   = machine.PA22
+	rx   = machine.PA23
+
+	console = machine.UART0
+
+	adaptor *espat.Device
+)
+
+func main() {
+	uart.Configure(machine.UARTConfig{TX: tx, RX: rx})
+
+	// Init esp8266/esp32
+	adaptor = espat.New(uart)
+	adaptor.Configure()
+
+	// first check if connected
+	if adaptor.Connected() {
+		console.Write([]byte("Connected to wifi adaptor.\r\n"))
+		adaptor.Echo(false)
+
+		connectToAP()
+	} else {
+		console.Write([]byte("\r\n"))
+		console.Write([]byte("Unable to connect to wifi adaptor.\r\n"))
+		return
+	}
+
+	// now make TCP connection
+	ip := espat.ParseIP(serverIP)
+	raddr := &espat.TCPAddr{IP: ip, Port: 8080}
+	laddr := &espat.TCPAddr{Port: 8080}
+
+	console.Write([]byte("Dialing TCP connection...\r\n"))
+	conn, _ := adaptor.DialTCP("tcp", laddr, raddr)
+
+	for {
+		// send data
+		console.Write([]byte("Sending data...\r\n"))
+		conn.Write([]byte("hello\r\n"))
+
+		time.Sleep(1000 * time.Millisecond)
+	}
+
+	// Right now this code is never reached. Need a way to trigger it...
+	console.Write([]byte("Disconnecting TCP...\r\n"))
+	conn.Close()
+	console.Write([]byte("Done.\r\n"))
+}
+
+// connect to access point
+func connectToAP() {
+	console.Write([]byte("Connecting to wifi network...\r\n"))
+	adaptor.SetWifiMode(espat.WifiModeClient)
+	adaptor.ConnectToAP(ssid, pass, 10)
+	console.Write([]byte("Connected.\r\n"))
+	console.Write([]byte(adaptor.GetClientIP()))
+	console.Write([]byte("\r\n"))
+}