Hi all,

I'm going to build an Ardu-Survey-Boat fro 3d bottom mapping based on this hardware:


APM 2.5

120A esc with Sbec 6V regultated at 5V to meet AMP compl.

9ch WFLY radio with Jeti RX PPM SUM

Boat Hull Surge Crusher EP XXL with Steering servo and Brushless motor

CruzPro Echosounder ATU120BT  for depth readings

3DR leah GPS

Xbee Pro 900 mhz telemetry


What I need to know if there is an usable serial port (UART) on the AMP2.5 as the echosounder data comes from a 232 serial on  nmea0183  format, I make a rs232/TTL converter for this.


I notice looking at eagle shematics that serial2 (pin 12 and 13 on  Atmega) is connected to output spare pin and to the MUX pad. I hope that as I use the MUX function between telemetry and USB I can use the serial2 for the echosounder.


If someone can confirm this I'll be happy :-)


Also some suggestion on how to enable and setup the baudrate of the serial2 will be appreciated, I have ready a library to parse the simple nmea string coming from the echo.


Thanks in advanced



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You can use UART0 for both USB and telemetry. The "mux" will switch UART0 between the extra little ATMega that does USB, and the UART0/2 connector on the board; connect the telemetry radio there. Those solder jumpers to switch the connector between "mux" and UART2 must then be connected to "mux". The multiplexing logic even switches the baud rate of UART0 between 110200 for USB and that set for UART3 (yes, three!) for telemetry.
 Then you can connect your echo sounder to the dedicated UART2 rx and tx pins at the side of the board.

Why UART3 is no available on APM2, I don't know. I have asked in the forum.

If someone can confirm this I'll be happy :-)

Confirmed. Just to make sure: The mux is purely a UART0 thing. Using it will leave UART2 free for you to use.



Hi Soren,

Thanks for the clarification, I've made some test and found that Uart2 is free if you maintein the mux on Uart0 between USB and Telemetry.

I think Uart3 is reserved on Apm2 to link the microprocessor to the ppm decoder that is another micro... I'm not 100% sure about it





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