This Wiki page provides a detailed guide on how to setup and operate PixArt's PMW3901MB sensor with any mBed-supported microcontroller.

• See https://os.mbed.com/platforms/ for supported boards.

Hardware¶

NOTE: This image shows the Nordic nRF52-DK microcontroller as an example.

• 1.) PC with Windows Operating System
• 2.) Any Microcontroller & Associated Cables (often USB-A male to USB-B male or USB-A male to micro-USB male)
• 3.) PMW3901MB Evaluation Board
• 4.) Jumper Cables
  
  • NOTE: PC not included in image.

Importing Code¶

First, we need to import code into the microcontroller to start talking to the sensor. For the firmware code, please visit this product's components page here:
https://os.mbed.com/components/PMW3901MB-Far-Field-Optical-Motion-Track/

• 1.) Login/create an mBed account.
  
  
• 2.) Import the reference firmware into mBed's online compiler using the "Import program" button. You can find this in the link above.
  
  
• 3.) When importing the program, make sure you import it as a program and not a library.
  
  
• 4.) Make sure the selected platform is the platform that you are using.
  
  
• 5.) Make sure your microcontroller is plugged into your PC. It should show up as a separate drive similar to the (C:) drive. Then, you can compile the program and save the HEX file into your microcontroller.
  • NOTE: If you suspect your code did not import properly, please try unplugging the device, plugging it back in, and then re-compiling and saving the code into the device.

Connection¶

Please refer to the images and notes below for details on how to connect your hardware.


The above images show how the sensor connects to the Nordic nRF52-DK as a template. To connect it to your own microcontroller of choice, please follow these steps:

• 1.) First make sure you have chosen the platform that you have. See step 4 in the "Importing Code" section.
• 2.) Assign any GPIO pins on your microcontroller to the SPI pins you want.
  • Change "static SPI spi(p23, p24, p25);" to "static SPI spi( [any_pin], [any_pin], [any_pin] );"
    • You will also need to change "static DigitalOut cs(p22);" to "static DigitalOut cs( [any_pin] );"
• 3.) With pins properly assigned, simply use jumper cables to connect them to the corresponding pins on the PMW3901MB evaluation board.
  
  ===Other notes:===
  
• VDDIO on the PMW3901MB evaluation board connects to any 3.3V pin (usually VDD) on your microcontroller.
• GND on the PMW3901MB evaluation board connects to any GND pin on the Nordic nRF52 microcontroller.
• NC = No connection.
• VDD on the PMW3901MB evaluation board connects to any 1.8V - 2.1V pin on your microcontroller.
  • NOTE: You may need an external power source to power the 1.8V - 2.1V rail for VDD on the PMW3901MB evaluation board. This is because some microcontrollers cannot be programmed to provide an analog output in this range.

Functional Test¶

• 1.) You will need a terminal emulator program. The one used in this guide will be Tera Term. If you do not already have it, you can find it at this link:
  https://en.osdn.jp/projects/ttssh2/releases/

• 2.) Open Tera Term and go to File > New Connection or use the hotkey "Alt + N". Select "Serial" and choose the COM port corresponding to your microcontroller. Then click on "OK".
  
  
• 3.) Go to Setup > Serial Port and set the baud rate to 115200. Then click on "OK".
  
  
  
• 4.) Go to Setup > Terminal and change "Receive" from "CR" to "LF". Then click on "OK".
  
  
  
• 5.) With the hardware wired up properly, the firmware loaded into the microcontroller, and the terminal emulator set up, we should now be able to see the sensor working. If you move your finger in front of the sensor (remember the working distance is 80mm to infinity), you should see outputs on the terminal:
  • "deltaX" and "deltaY" show the number of counts detected per report.
  • "X-axis Counts" and "Y-axis Counts" show the total number of counts recorded throughout runtime.

Thank you for choosing PixArt! If you have any questions, feel free to contact us at: sales_us@pixart.com.