The mangoh dev platform has an Arduino Leonardo connected to a WP module. The default configuration has the two connected via WP:USB <-> FTDI <-> Arduino:UART. I wanted to connect UART-to-UART, and these are the steps to do that.

1. There is an analog switch that needs to be rerouted.

   

2. The FTDI chip needs to be tri-stated to avoid pulling up the RX line

   

   The purple circles show the location of those shorts on the bottom layer of the mangoh’s solder mask gerber.

   

3. On the WP shell, which is accessible via the on-board DB-9 serial connector or via ethernet¹, you need to enable the uart.

microcon /dev/ttyAT
AT!MAPUART=17,1
OK

And you are done. To test…

1. Write a character echo program such as:

#! /bin/sh

stty -F /dev/ttyHSL0 115200
stty -F /dev/ttyHSL0 -echo

while read X
do
echo Got: $X, echoing back $X
echo $X > /dev/ttyHSL0
done < /dev/ttyHSL0

and execute

./echo_data.sh

1. And program the Arduino to bridge the USB serial consosole to the UART port

void setup() {
Serial1.begin(115200);
}

void loop() {
char oneChar;

while (Serial.available() > 0) {
	// read the incoming byte:
	oneChar = Serial.read();
	Serial1.print(oneChar);
}

while (Serial1.available() > 0) {
	// read the incoming byte:
	oneChar = Serial1.read();

	// print locally what you got
	Serial.print(oneChar);
}
delay(1000);
}

1. Now fire up the Arduino terminal and you should see characters echoed back to you.

   

1: A gotcha using Ethernet: the WP is configured with DHCP, but it will choose a random mac address after each reboot. So you will have to find its IP address on every reboot until you disable that behavior (which I don’t know how to do).