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How to read two I2C (Having Same Address) sensors using NRF52840

Khalil Ahmad

Hi All,

I have a custom board where I have connected Two Sensors MAX86916 to the 0.26 and 0.27 pins of NRF52840. When I tried to scan it only shows one address 0x57. I want to use both sensors. 

To counter check my setup I use NRF52840 SDK and connected two different sensors and then scanned it show both sensors address separately.

My question is how can I get the data of both sensors even at the same time or different time. My intention is to get the sensor data of both sensors. Can I get the data of both sensors from single address ???? If not, what are the possible solution to get the data of both sensors even by software or hardware modifications.

 

  • 0

    Hi,
    See https://learn.adafruit.com/working-with-multiple-i2c-devices/overview for a guide on multiple I2C devices with the same address

    Often, I2C slave ICs have a pin which can toggle between giving it different addresses.
    For example from MC3479:

    Regards,
    Sigurd Hellesvik

  • 0 in reply to Sigurd Hellesvik

    This is the link of the datasheet 

    Data Sheets-max86916

    I read the information provided in the link. as per my custom PCB both sensors are connected on the same pin but their interrupt is at different pins. I checked the PCB and

    1 - Its not possible to make any changes physically to disconnect the pins and connect to other pins

    2 - There is no information for selecting different address

    My Question is... If nothing works then what happened now ?? Means to say as both sensors are connected with same address (The purpose of using two sensors to locate the vein to check the pulse... any of the sensor will find it and give the result). Its mean both sensors will send the data on single address. 

    After reading the Data Sheet I came to know that there is proximity option (which means when its enabled, the sensor will start its operation when detects the pulse)

    and

    and 

    As per the proximity enable option. Lets assume if any of the sensor (the other will be in the idle mode) find the vein, so I will get the data ?????

  • 0 in reply to Khalil Ahmad
    Khalil Ahmad said:
    My Question is... If nothing works then what happened now ?? Means to say as both sensors are connected with same address (The purpose of using two sensors to locate the vein to check the pulse... any of the sensor will find it and give the result). Its mean both sensors will send the data on single address. 

    Could look like that. I assume that you have no way to disconnect one of the sensors from power?

    Khalil Ahmad said:
    As per the proximity enable option. Lets assume if any of the sensor (the other will be in the idle mode) find the vein, so I will get the data ?????

    Are the sensors interrupts routed to different pins on the nRF?

    Khalil Ahmad said:
     Lets assume if any of the sensor (the other will be in the idle mode) find the vein, so I will get the data ?????

    Well, if I2C wakes up the sensor as well, this will not work. I struggle to find if this is the case from the datasheet or not.

  • 0 in reply to Sigurd Hellesvik

    Yes, Interrupts are routed to different pins on the NRF52840.

  • 0

    Bad idea. These require quite a bit of bus bandwidth in order to read all the FIFO data.

    Use a set of pins for each sensor, the NRF52840 has two TWIM uinits. That allows you to read the data in parallel.

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