Hello!
I have trouble to use the Softwire library on the Arduino Nano 33 BLE Boards.
First things first: I need to use all analog Pins of the BLE 33. I also use some I2C devices. So I decided to use the Softwire library for software-I2C connectivity of the SDA, SCL pins. I've used this library often in the past with the old Arduino Nano, which worked very well.
The following notice on the Arduino BLE 33 website confused me: "I2C pins: As opposed to other Arduino Nano boards, pins A4 and A5 have an internal pull up and default to be used as an I2C Bus so usage as analog inputs is not recommended."
Still, i've installed a test script and tried to connect to my I2C devices (MPU 6050 and DS3231) via pin 6 and 7. Therefor I've modified the first ~10 lines of the standard i2c-scanner example with the Softwire-library and added some buffers:
// --------------------------------------
// i2c_scanner
//
// Version 1
// This program (or code that looks like it)
// can be found in many places.
// For example on the Arduino.cc forum.
// The original author is not know.
// Version 2, Juni 2012, Using Arduino 1.0.1
// Adapted to be as simple as possible by Arduino.cc user Krodal
// Version 3, Feb 26 2013
// V3 by louarnold
// Version 4, March 3, 2013, Using Arduino 1.0.3
// by Arduino.cc user Krodal.
// Changes by louarnold removed.
// Scanning addresses changed from 0...127 to 1...119,
// according to the i2c scanner by Nick Gammon
// https://www.gammon.com.au/forum/?id=10896
// Version 5, March 28, 2013
// As version 4, but address scans now to 127.
// A sensor seems to use address 120.
// Version 6, November 27, 2015.
// Added waiting for the Leonardo serial communication.
//
//
// This sketch tests the standard 7-bit addresses
// Devices with higher bit address might not be seen properly.
//
#include <SoftWire.h>
SoftWire Wire {6, 7}; // {SDA, SCL}
byte rxBuffer[32];
byte txBuffer[32];
void setup()
{
Serial.begin(9600);
Serial.println("\nI2C Scanner");
Wire.setRxBuffer(rxBuffer,sizeof(rxBuffer));
Wire.setTxBuffer(txBuffer,sizeof(txBuffer));
Wire.begin();
}
void loop()
{
byte error, address;
int nDevices;
Serial.println("Scanning...");
nDevices = 0;
for(address = 1; address < 127; address++ )
{
// The i2c_scanner uses the return value of
// the Write.endTransmisstion to see if
// a device did acknowledge to the address.
Wire.beginTransmission(address);
error = Wire.endTransmission();
if (error == 0)
{
Serial.print("I2C device found at address 0x");
if (address<16)
Serial.print("0");
Serial.print(address,HEX);
Serial.println(" !");
nDevices++;
}
else if (error==4)
{
Serial.print("Unknown error at address 0x");
if (address<16)
Serial.print("0");
Serial.println(address,HEX);
}
}
if (nDevices == 0)
Serial.println("No I2C devices found\n");
else
Serial.println("done\n");
delay(5000); // wait 5 seconds for next scan
}
But I can't find any devices. The searching is working well (I have investigate the pins with Logic-Adapter). Also the signals are looking good on my scope.
When change the code to the normal i2c-scanner-example (normal Wire-library) and connect my devices to pin 4 and 5, everything is working well...
Thus, it is really not possible to connect my I2C devices to other digital pins on the Nano BLE 33? And what about the "internal pullup resistors"? They must be inside the nordic-board (because there are no other pullups on the Arduino PCB design...?). In (my) conclusion, pin A4 and A5 is useless for analog readings and are reserved for I2C connections...? That would be too bad...
Maybe someone can give me a hint? Thanks a lot!
Regards,
Klaus
