I've got an Arduino V3+ and need to find the correct PIN number for its RX and TX-pin on the FTDI-connector.

How can I find out the correct number of them to use them with the SoftwareSerial-library?

Why I need these numbers:

I'm connecting a Sparkfun Bluetooth Mate/BlueSMIRF to the ArduiMUs FTDI headers and need to set a few settings in its command mode before it operates without flaws. This is the code I'm using:

#include <SoftwareSerial.h>

int bluetoothTx = ???;  // TX-O pin of bluetooth mate, Arduino D2
int bluetoothRx = ???;  // RX-I pin of bluetooth mate, Arduino D3
SoftwareSerial bluetooth(bluetoothTx, bluetoothRx);

void setup()
  Serial.begin(9600);  // Begin the serial monitor at 9600bps

  bluetooth.begin(115200);  // The Bluetooth Mate defaults to 115200bps
  bluetooth.print("$$$");  // Enter command mode
  delay(5000);  // Short delay, wait for the Mate to send back CMD
  bluetooth.println("U,9600,N");  // Temporarily Change the baudrate to 9600, no parity
  // 115200 can be too fast at times for NewSoftSerial to relay the data reliably
  bluetooth.begin(9600);  // Start bluetooth serial at 9600

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1 Answer 1


You can use FTDI cable with your board on the last row of pads as you have highlighted.

Unfortunately your board designers do not publish a pdf version of the schematic so I opened the provided schematics in EAGLE and exported the FTDI connector diagram.

Here is the FTDI connector connections from the schematic:


Here is the pinout of the FTDI cable

FTDI Cable

So you can solder a 6 pin header on the bottom row and use the standard FTDI cable.

The FTDI row on your board indicates "BLK" on the left so orient your FTDI connector's black wire with the "BLK" pad on your board.


As per your edits you are using hardware serial on your arduino board to monitor and you are using one instance of "SoftwareSerial" to interface with bluetooth.

As SoftwareSerial library says, you can define any digital pins for Tx and Rx. In the example they have used Arduino pins 10 (pin 14 of the ATMEGA) and 11 (pin 15 of ATMEGA) for Rx and Tx respectively. In your non-standard arduino board, the micro-controller pin 14 is labeled as PWM1 and pin 15 is labeled as MOSI and they are brought out on connector JP7.


So in a nutshell you can use pin 4 of JP7 as SoftRx and pin 5 of JP7 as SoftTx.

If those pins are in use, you can always use other digital pins that are unused in your design. Just refer to the schematic of your board, ATMEGA328 datasheet and arduino libraries.

  • Thanks for your effort. I'm already using a FTDI cable to put Arduino Software on it. I need to know to RX & TX pin mumber because I connect a Bluetooth module (FTDI compatible) and need to send a few messages to it (it is a Bluetooth Mate Silver and has a command mode). I need the pin numbers to communicate via ArduiMu with the Bluetooth module.
    – Hedge
    Jun 18, 2015 at 4:34
  • @Hedge pin number of what? ATMEGA device? pin number of board? pin number of FTDI cable? Please clarify your question. Thanks. Jun 18, 2015 at 6:38
  • Sorry for the confusion. I need the PIN number of the RX and TX pin on the Arduino board to write to the TX channel and receive data from the RX channel of the ArduiMU overall. The SoftwareSerial-library needs the port numbers of them to operate SoftwareSerial mySerial(10, 11); // RX, TX
    – Hedge
    Jun 18, 2015 at 10:16
  • I added the code I need the PIN-numbers for to the original question. You should be able to better understand what I'm trying to do.
    – Hedge
    Jun 18, 2015 at 10:58
  • @Hedge now I understand that you are using the main ftdi port to monitor and want to use another serial port for bluetooth. Is that correct? Jun 18, 2015 at 18:32

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