Serial interface not working

Hi All,

I have a Swan plugged into a Notecarrier F. The I²C interface is working fine if I use the code from the example:


If I change it to:

notecard.begin(Serial1, 9600);

It doesn’t work at all. One thing is that I have the onboard LED turned on when operations are happening. With the I²C interface, the LED flicks on very briefly, as one would expect. With the serial interface it stays on for maybe two seconds. The code resumes but it is clear that the operation is failing.

I tried buzzing out the TX and RX pins on the Swan to N_RX and N_TX pins on the Notecarrier and there is no apparent connection. I had previously used the N_RX and N_TX pins to communicate with the Notecard.

Am I missing something?

Thanks in advance,


Hi Rob,

There are no traces between the Notecard and Feather on the Notecarrier-F.

If you want to use serial, then you will need to run jumpers between the two as shown in the table below:

Notecard Feather

Also, be sure to set the DFU switch (near the Notecard socket) to the OFF position (i.e. nearest the DFU label, away from ON).

Then you should be able to send transactions over Serial.

Happy Hacking,

1 Like

Hi Zak,

Thanks for the quick reply.

Does that mean I will not be able to use OTA updates if I use the serial interface?

If that is the case I will keep using the I²C interface. It seems to work OK but I haven’t tried it with my 2000+ character strings yet.



Yes, that is correct.

I believe I may have mislead you on a different thread.

Theoretically, you can wire up a mux based on AUX1. It serves as a signal for when a DFU is taking place. The pin is described in the Notecard Outboard Firmware Update Guide.

I would encourage you to first profile the transfers and see if you can find success on the path supported by the existing hardware on the Notecarrier-F.



I haven’t used the Swan board, but I’m using an ESP32 Feather board on the Notecarrier-F, I have Outboard Firmware update working and I’m using a second serial port to communicate over an RS-232 to RS-485 converter. The ESP32 Feather board used Serial0 for serial Outboard Firmware update and Serial1 for the RS-232/RS-485 converter.

If the Swan doesn’t support two serial ports, you can switch to a different Feather board and get the desired results without have to build a mux as Zak indicated.


Hi Karl,

That is interesting. I have a Huzzah board around somewhere. I thought of using it as a Bluetooth interface.

On paper, the Swan has more than two serial ports. Today I am adding the code that uses Serial2. I will soon find if it works.