wifinina: add information about Adafruit boards with ESP32 wifi coprocessors, and modify examples to remove code that was both not being used, and also prevented many Adafruit boards from being able to be targeted by the examples

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

examples/wifinina/mqttclient/main.go

@@ -35,10 +35,7 @@ const server = "tcp://test.mosquitto.org:1883"
 var (
 
 	// these are the default pins for the Arduino Nano33 IoT.
-	uart = machine.UART2
-	tx   = machine.NINA_TX
-	rx   = machine.NINA_RX
-	spi  = machine.NINA_SPI
+	spi = machine.NINA_SPI
 
 	// this is the ESP chip that has the WIFININA firmware flashed on it
 	adaptor *wifinina.Device
@@ -48,7 +45,6 @@ var (
 func main() {
 	time.Sleep(3000 * time.Millisecond)
 
-	uart.Configure(machine.UARTConfig{TX: tx, RX: rx})
 	rand.Seed(time.Now().UnixNano())
 
 	// Configure SPI for 8Mhz, Mode 0, MSB First
@@ -94,7 +90,7 @@ func main() {
 				println(err.Error())
 			}
 		}
-		time.Sleep(1 * time.Millisecond)
+		time.Sleep(100 * time.Millisecond)
 	}
 
 	// Right now this code is never reached. Need a way to trigger it...