Connection Error

[batulaiko]

Hi i wrote a simpel code to check is it work or not. when m=max30102.MAX30102(), it prints (Channel = 1 , Address 87) and stucks in red, ir = m.read_sequential part. I checked in i2cdetect -y 1 , it shows the address 57. But in code, it is 87. The connections are true by the way.

I have 7 pin version but I think it doesn't matter it is 5 or 7 pin.

Do you have any idea about that?

Have a nice day.

[vrano714]

Hi, batulaiko.

Initialization of the sensor is written here:

class MAX30102():
    # by default, this assumes that physical pin 7 (GPIO 4) is used as interrupt
    # by default, this assumes that the device is at 0x57 on channel 1
    def __init__(self, channel=1, address=0x57, gpio_pin=7):
        print("Channel: {0}, address: {1}".format(channel, address))
        self.address = address
        self.channel = channel

As you can see, the address to be printed is decimal format, because no formatting is set here. Therefore, 0x57 is shown as 87. (0x57 = 5x 16 + 7 = 87) I guess the connection is successful.

---

Sensor reading is as:

    def read_sequential(self, amount=100):
        """
        This function will read the red-led and ir-led `amount` times.
        This works as blocking function.
        """
        red_buf = []
        ir_buf = []
        for i in range(amount):
            while(GPIO.input(self.interrupt) == 1):
                # wait for interrupt signal, which means the data is available
                # do nothing here
                pass

            red, ir = self.read_fifo()

            red_buf.append(red)
            ir_buf.append(ir)

        return red_buf, ir_buf

This code waits until the data becomes available and availability is notified via interrupt pin. Please ensure that 5 pins (Vin, SDA,SCL, INT, GND) of your HR sensor are correctly connected to corresponding RaspberryPi pins. (I do not have 7pin version, so I do not know its pin assign. sorry)

[vrano714]

FYI: I updated max30102.py to show hex address (commit 8a80db7).

[batulaiko]

I can use max30100.py in another respiratory. I can get values from them. I am using 5 pin actually. There are 7 pins but I am using Vin, SDA,SCL, INT, GND pins. It shows me address is 0x57 now but still stucks in data reading.

This is the code which I am using. I put some prints for being sure the function which makes stucking this code.

I can use max30100.py in other respiratory but I need to figure the HR calculation function out.

Simply, for calculation, I need a list which contaions 100 data which appended 25 sample rate, am I right?

If I change sample rate, is the fuction be affected because of it?

[vrano714]

Your code looks good.

Can you see red light from the sensor? Working sensor should emit red light (and IR light, which we cannot see). If yes, I cannot figure out why. Sorry.

This repository contains a modified version of max30102 to free from INT pin. I do not know whether this works, but if you are interested, please try it. https://github.com/doug-burrell/max30102

---

Simply, for calculation, I need a list which contaions 100 data which appended 25 sample rate, am I right?

Yes. hrcalc.py do some peak detection on its input signal to calc heart rate. You can use the data recorded by other (similar) sensors.

If I change sample rate, is the fuction be affected because of it?

Yes. hrcalc.py has the following constants: SAMPLE_FREQ and BUFFER_SIZE. If you feed the data with different frequency than 25 Hz, please set appropriate values on them.

SAMPLE_FREQ is just a sampling frequency. For example set 100 if you feed 100 Hz data. BUFFER_SIZE should be set to 4*SAMPLE_FREQ. (I just follow the original Arduino code. I do not know why, however it seems that 4-sec data is needed, not 100)