German Rivera

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6 years, 7 months ago.

Not able to access the heart rate monitor in the Hexiwear board

I'm having problems accessing the heart rate monitor in the Hexiwear board. I'm able to talk to other I2C devices on the board such as the accelerometer and the barometric pressure sensor. So, the problem does not seem to be in my I2C driver. I wonder if I need to do a hard reset of the heart rate monitor chip first. However, according to the schematics, there is no reset pin for the heart rate monitor. The sample code from NXP does seem to indicate that pin PTA29 is a Power pin for the Heart rate monitor. However, the schematics does not show that. Anyway, I tried using this pin in the same way as the NXP sample code, but still no luck. I2C communication still fails.

Any pointers to relevant information of how enable and access the Hexiwear's heart rate monitor would be highly appreciated

Thanks,

German

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Last updated: 27 Aug 2020
Next generation wearable IoT development platform designed to reduce time to market. Comes in compact form factor with on-board MCUs, BLE connectivity, sensors, OLED display, and battery. Open source software …

2 Answers

Anass KAZIZ
6 years, 5 months ago.

Hi German,

I really have the same problem. I'm able to talk with other devices, but not to the heart rate sensor.

Did you find any solution ?

Thanks.

Anas

Riccardo Mastronardi
6 years, 4 months ago.

Hi German, as you've read in the sample code you need to power up the MAX30101 before trying to talk to it through the I2C. This is achieved by creating a DigitalIn on the PTA29, as you said, and setting it to 1. Just like you, I couldn't find any reference as to where that information came from, until I looked through the schematics, which are at this address: https://os.mbed.com/media/uploads/GregC/sch_hexiwear_mainboard_v106.pdf If you go to page 11 you'll find all the powering voltages explained. If you need to find how to power up any sensor (the MAX30101 and all the sensors on the second I2C channel need to be powered up), this is where you'll find the info you're looking for: look at your sensor in that file and find what voltage it's connected to it, and then look for it at page 11 and you'll find what pin activates it and if it's on HIGH or LOW logic. In the case of the MAX30101, as I wrote before, it's with HIGH logic, so you need to set the pin to 1.

Hope of having helped you. Riccardo