[Feature Request] Add SoftwareSerial / Uart lib to Nano 33

[pierre-b]

Hello Arduino,

For an IoT project I need to connect a GPS and GPRS board, each needs a Serial port.

As there is only one Serial port available (the USB is taken) I need a second Serial port. Unfortunately SoftwareSerial and Uart libs don't work on Nano 33 and I'm stuck.

Is it something you could add? or clearly I can't build my project with a Nano 33?

Thanks

ping @ostaquet

[per1234]

Which Nano 33 are you using, the Nano 33 IoT or the Nano 33 BLE/BLE Sense?

[pierre-b]

It's BLE Sense

[facchinm]

Hi @pierre-b ,
Nano 33 BLE has a second serial port (as Serial1) on pins 0 and 1. You can use it to communicate with the GPS. If the library you are using is not compiling please add some info here (like the hardware you are targeting and the library name and version)

[pierre-b]

Hi @facchinm , yes I meant Serial1 when I said:

there is only one Serial port available

So I would need a Serial2 or SoftwareSerial / Uart libs. I didn't express myself clearly.

Are SoftwareSerial / Uart libs a possibility in the near future or should I ditch the Nano 33 BLE?

Thanks

[facchinm]

Got it, sorry for the confusion. nRF52480 has support for two hardware UART; we are using just one (on pins 0 and 1) but you can easily instantiate another.
Two methods: changing the core with the following patch

diff --git a/variants/ARDUINO_NANO33BLE/defines.txt b/variants/ARDUINO_NANO33BLE/defines.txt
index e995d15e..2365b15e 100644
--- a/variants/ARDUINO_NANO33BLE/defines.txt
+++ b/variants/ARDUINO_NANO33BLE/defines.txt
@@ -21,7 +21,7 @@
 -DDEVICE_PORTINOUT=1
 -DDEVICE_PORTOUT=1
 -DDEVICE_PWMOUT=1
--DDEVICE_SERIAL=1
+-DDEVICE_SERIAL=2
 -DDEVICE_SERIAL_ASYNCH=1
 -DDEVICE_SERIAL_FC=1
 -DDEVICE_SLEEP=1
diff --git a/variants/ARDUINO_NANO33BLE/pins_arduino.h b/variants/ARDUINO_NANO33BLE/pins_arduino.h
index 5937dba1..3ff156e6 100644
--- a/variants/ARDUINO_NANO33BLE/pins_arduino.h
+++ b/variants/ARDUINO_NANO33BLE/pins_arduino.h
@@ -60,6 +60,9 @@ static const uint8_t A7  = PIN_A7;
 #define PIN_SERIAL_RX (1ul)
 #define PIN_SERIAL_TX (0ul)
 
+#define PIN_SERIAL1_RX (3ul)
+#define PIN_SERIAL1_TX (4ul)
+
 // SPI
 #define PIN_SPI_MISO  (12u)
 #define PIN_SPI_MOSI  (11u)
@@ -111,9 +114,11 @@ static const uint8_t SCK  = PIN_SPI_SCK;
 
 
 // Mbed specific defines
-#define SERIAL_HOWMANY         1
+#define SERIAL_HOWMANY         2
 #define SERIAL1_TX                     (digitalPinToPinName(PIN_SERIAL_TX))
 #define SERIAL1_RX                     (digitalPinToPinName(PIN_SERIAL_RX))
+#define SERIAL2_TX                     (digitalPinToPinName(PIN_SERIAL1_TX))
+#define SERIAL2_RX                     (digitalPinToPinName(PIN_SERIAL1_RX))
 
 #define SERIAL_CDC                     1
 #define HAS_UNIQUE_ISERIAL_DESCRIPTOR

(you can change PIN_SERIAL1_RX / PIN_SERIAL1_TX as you prefer 🙂 )

or from the code, inside the sketch

UART mySerial(digitalPinToPinName(4), digitalPinToPinName(3), NC, NC);

(change 4 and 3 as you prefer, the processor can mux any functionality on any pin)

[pierre-b]

Thank you @facchinm , will those modifications to the core be released officially?

Also, does the "UART mySerial(..." config work without modifiying the core?

[facchinm]

The UART mySerial(... works without any core modification.
We will never release the core patch because it would limit user freedom to move the pins wherever s/he needs

[zungun]

diff --git a/variants/ARDUINO_NANO33BLE/defines.txt b/variants/ARDUINO_NANO33BLE/defines.txt

where can i find this route??

[Maximumotion]

Hello Arduino,
I wanted to ask if the method of adding the second serial to Arduino Nano 33 BLE IoT is the same as describe in the above topic.
I am connecting a Nextion Display to the board and also using GPS so trying to figure out how to add the second serial.
thanks

[facchinm]

Hi @Maximumotion ,
do you mean Arduino Nano 33 IoT? In that case, the reference method to add a second serial port is explained here

[Maximumotion]

Thank you for your reply!
Yes, I meant Arduino Nano 33 IoT.
Just to make sure I understood it right as its quite technical. On the page with the explanation there was a reference to a variant.cpp file that is specific to the board.
Looking to the variant.cpp for Arduino Nano 33 IoT, I can see there are 2 serials:
Uart Serial1( &sercom5, PIN_SERIAL1_RX, PIN_SERIAL1_TX, PAD_SERIAL1_RX, PAD_SERIAL1_TX ) ;
and
Uart Serial2(&sercom3, PIN_SERIAL2_RX, PIN_SERIAL2_TX, PAD_SERIAL2_RX, PAD_SERIAL2_TX);

So by default, Arduino Nano 33 IoT has Serial1 set to pin 0 and 1.
Based on explained in provided resources, If I want second Serial on pins 3 and 2, it would look something like this?

Uart mySerial (&sercom3, 3, 2, SERCOM_RX_PAD_3, UART_TX_PAD_2);

Thank you!

[facchinm]

@Maximumotion Nano33IoT is already using sercom 2,3,5 internally (https://github.com/arduino/ArduinoCore-samd/blob/master/variants/nano_33_iot/variant.cpp#L188-L207) , so you need to check these lines to find the supported sercom (if it exists).
In this case we are lucky and it's sercom4, but you would lose I2C since it uses the same port (https://github.com/arduino/ArduinoCore-samd/blob/master/variants/nano_33_iot/variant.h#L154).

In the end, your extra serial port becomes

Uart mySerial (&sercom4, 3, 2, SERCOM_RX_PAD_3, UART_TX_PAD_2);