Nano RP2040 multiple sensor data separation

@snb

The I2C protocol requires that each address has a separate address to which commands are sent and data is received.

It appears that the sensor you have selected has only a fixed address, 0xAE for write operationsand 0xAF for read operations. Since it seems that the manufacturer has left no way to change the address to differentiate the sensors to the uController, you will need to make significant changes to your design.

This old video may explain it and a possible solution for you.

@snb @will FYI EDIT My bad, I see @will covered it. Hey, I haven't had my first coffee, just ignore the old man behind the curtain.

Another possible approach is an I2C multiplexor like

https://learn.adafruit.com/working-with-multiple-i2c-devices

or find a board that can house your board and provide multiple I2C. I am sure I have seen one but don't remember where and in any case is probably just a packaged multiplexor/rp2040 board.

Thanks, @Will and @Ron for the super fast response. Will try out and revert. 

@snb I assume that was supposed to be ... and report.

Hi @snb,

 I haven't watched them, but in addition to the video @will mentioned, there are others, probably all based on the device, although they may have different boards:

From this forum, Bill (aka @drone-workshop) 's excellent clear style and guaranteed to work approach:

...............

And for further views, since it sometimes it pays to watch more than one to pick up small details, etc.

'Randon Nerd Tutorials' crowd usually do their homework and worth a look:

https://randomnerdtutorials.com/tca9548a-i2c-multiplexer-esp32-esp8266-arduino/

And similarly, the "Guy with Swiss accent"

www.youtube.com/watch?v=QQLfzlPGjjE

Best wishes, Dave

Thanks @DaveE for all the help extended.

While I am waiting for the multiplexer to be delivered, I will explore the software options. The homemade I2C bus is an interesting concept that I may use it for some other project. 

@zander yes

Here is an update. I am using PCA9548A multiplexer. SDA of MUX is connected to A4, SCL is connected to A5 of Nano rp2040. PIN A0, A1, A2 of MUX are grounded. sensor 1 SDA and SCL are connected to SD0 and SC0, and Sensor 2 SDA and SCL are connected to SD1 and SC1 of MUX. The sensors are not getting detected. I tried running I2C scanner. As long as I connect only RP2040, the scanner detects two addresses 0x60 and 0x6A. when I connect the mux, the scanner gets into an infinite loop and doesn't display anything until I disconnect the MUX. where am I going wrong?

#include <Wire.h>
#include "MAX30105.h"
#include "spo2_algorithm.h"
#include "heartrate.h"
#include "WiFiNINA.h"

MAX30105 sensor1;
MAX30105 sensor2;

const byte RATE_SIZE = 4;
byte rates[RATE_SIZE];
byte rateSpot = 0;
long lastBeat = 0;
float beatsPerMinute;
int beatAvg, perCent1, iroffset1 = 2100;

#if defined(__AVR_ATmega328P__) || defined(__AVR_ATmega168__)
//Arduino Uno doesn't have enough SRAM to store 100 samples of IR led data and red led data in 32-bit format
//To solve this problem, 16-bit MSB of the sampled data will be truncated. Samples become 16-bit data.
uint16_t irBuffer[100]; //infrared LED sensor data
uint16_t redBuffer[100];  //red LED sensor data
#else
uint32_t irBuffer[100]; //infrared LED sensor data
uint32_t redBuffer[100];  //red LED sensor data
#endif

int32_t bufferLength; //data length
int32_t spo2; //SPO2 value
int8_t validSPO2; //indicator to show if the SPO2 calculation is valid
int32_t heartRate; //heart rate value
int8_t validHeartRate; //indicator to show if the heart rate calculation is valid

void TCA9548A(uint8_t bus){
  if(bus>7) return;
  Wire.beginTransmission(0x70);  // TCA9548A address
  Wire.write(1 << bus);          // send byte to select bus
  Wire.endTransmission();
  Serial.print(bus);
}

void setup()
{
  byte ledBrightness = 25;
  byte sampleAverage = 4;
  byte ledMode = 2;
  byte sampleRate = 400;
  int pulseWidth = 411;
  int adcRange =2048;
  
  Serial.begin(9600);
  //pinMode(A4, INPUT);
  //pinMode(A5, INPUT);

  Serial.println("Initializing...");
  Wire.begin();
  delay(0);

  //Sensor1
  TCA9548A(0);
  if(!sensor1.begin(Wire, I2C_SPEED_FAST)) {
    Serial.println(F("SENSOR 1 NOT DETECTED!! 1......1.....1......1......1......1"));
    for(;;);
  } 
  Serial.println("Place finger on sensor 1. ......1........1");
  sensor1.setup(ledBrightness, sampleAverage, ledMode, sampleRate, pulseWidth, adcRange);
  sensor1.setPulseAmplitudeRed(0x0A); //Turn Red LED to low to indicate sensor is running
  sensor1.setPulseAmplitudeGreen(0);//turn off Green LED

  //Sensor2
  TCA9548A(1);
  if(!sensor2.begin(Wire, I2C_SPEED_FAST)) {
    Serial.println(F("SENSOR 2 NOT DETECTED!! 2......2.....2......2......2......2"));
    for(;;);
  } 
  Serial.println("Place finger on sensor 2. ......2........2");
  sensor2.setup(ledBrightness, sampleAverage, ledMode, sampleRate, pulseWidth, adcRange);
  sensor2.setPulseAmplitudeRed(0x0A); 
  sensor2.setPulseAmplitudeGreen(0);
}

void loop()
{
  //Sensor 1
  TCA9548A(0);
  long irValue1 = sensor1.getIR();
  Serial.print(irValue1*5000);
  Serial.print(" ");
  
  //Sensor 2
  TCA9548A(1);
  long irValue2 = sensor2.getIR();
  Serial.print(irValue2);
  Serial.print(" ");
}

@snb My limited understanding of a multiplexor is it occupies one address on the MPU/MCU and by using a selector of some sort can connect the multiplexor to several I2C buses. That means the standard I2C scanner will not be able to 'see' the I2C devices connected to the mux, the scanner will only 'see' the mux which is itself not an I2C device.

I do not have detailed information or experience with a mux but would expect to see some code to cause the mux to select one of the downstream I2C devices at a time. I don't see anything like that.

I hope my naive observations spur you to more research and success.

Good luck.

EDIT Found a sample of how to select over on the nerds site, see pic, I recommend the randomnerds for inspiration.

@zander Thanks a lot for the reply. I have included the bus selection method before setup(). also, I am switching between bus0 and 1. 

@snb So it's working?

@zander no. Its not. I have connected the nano to laptop for power. I can measure 5V across nano, mux as well as sensor. If i connect Uno instead of nano, it works with following code. with Nano I tried with A4 and A5. but not able to get it working. 

pinMode(11, OUTPUT);
pinMode(13, OUTPUT);

@snb Maybe you should study their article and example and run their example on your board to make sure it's not a board problem, then you can modify that sketch to do whatever you want that is different.

Here is the link https://randomnerdtutorials.com/tca9548a-i2c-multiplexer-esp32-esp8266-arduino/

Dear @zander, The code looks different because of the sensor. I have followed the same code. I am able to read both sensor data through MUX if I am connecting Arduino Uno. but with nano, it fails. Even when I scan for I2C address, with Uno I get addresses 0x57 and 0x70. but Nano returns 0x60 and 0x6A. As I understand, these two (60 and 6A are reserved for the accelerometer and gyrometer). not able to understand the mistake.