1. Question: I'm unable to get heart rate information from the GUI.
Answer 1a: The MAXREFDES220 must be flashed with the Maxim supplied algorithm after it is purchased. See the Maxim website for obtaining the latest .msbl file.
MAXREFDES220 Design Resources, SW Packet
The flashing instructions are included in the software zip file.
Answer 1b: The GUI requires that the correct Mbed serial device driver is properly installed.
Click on this link for troubleshooting the Windows 7 and Windows 10 drivers.

2. Question: How do I design my own board which will use the smart sensor microcontroller and sensor?
Answer: The schematic for the MAXREFDES220 may be found at the Maxim website listed above. Note that the production part number for the microcontroller is MAX32664GWEA+.
The following are the necessary pin connections between the host and the MAX32664
Pin RSTN – RESET_N GPIO
GPIO P0_1 – MFIO GPIO
GPIO P0_2 – SCL (+pullup resistor)
GPIO P0_3 – SDA (+pullup resistor)
The following pins are also used between the MAX32664 and the sensors in the MAXREFDES220 design.
GPIO P0_6 – KX122 Accel Interrupt
GPIO P0_7 – MAX30101 Interrupt
GPIO P0_8 – MAX30101, KX122 I2C1_SCL
GPIO P0_9 – MAX30101, KX122 I2C1_SDA

3. Question: Where do I find sample host source code to the Smart Sensor?
Answer: The link is below:
Sample Host Code
Here's link to the host code which switches the MAXREFDES220 states from Bootloader/In-App Programming mode to Aplication mode:
SSInterface.cpp
Below is a link to the host code which parses the input commands to the host and translates those to I2c commands that the MAXREFDES220 accepts. A sample command to the host would be "get_reg ppg 0" to read register 0 of the MAXREFDES220.
SSMAX30101_Comm.cpp
Sample Host code for In-App Programming/Updating of the Maxim supplied .msbl algorithm firmware is at the following link:
SSBootloaderComm.cpp

4. Question: Where are the block diagrams, timing diagrams and interface definitions?
Answer: The link is below (at the Mbed Wiki for the MAXREFDES220).
MAXREFDES220 Block Diagram, Timing Diagrams, Interface Definitions, and I2C trace

5. Question: How do I download my own algorithm? How do I create my own sensor hub?
Answer: The MAXREFDES200/MAX32664 Smart Sensor only accepts Maxim supplied algorithms. In order to develop your own sensor hub, please use the low-power, low cost MAX32660 microcontroller and the Maxim supplied non-secure bootloader for the sensor hub.

6. Question: Why does the graph of the IR and Red Raw Data Count have an overall up and down drift to the waveform. when measuring HR?
Answer: When holding your finger on the sensor, there's minute variation in pressure which causes differences in the signal strength. The Maxim supplied algorithm is able to DC adjust for this variation when it calculates the Heart Rate.

7. Question: What are the headings for the logged data? Where is the log file stored?
Answer: Timestamp, IR Raw Counts, Read Raw Counts, unused, Accel X, Accel Y, Accel Z, HR, Confidence, SpO2.
The log file will be in the directory C:\MaximLogs

8. Question: How do I export the program to the PC for compiling with Keil uVision5, IAR ,GCC, Eclipse, E2 Studio, EmBitz, or Zip?
Answer: Instructions for exporting an Mbed program to your PC

9. Where is the MAX32664 User Guide.
- The CMD_DELAY in the User Guide should be 2 msec instead of 60 usec.
- When switching from Bootloader mode to Application mode, it takes 1 second for the Application to initialize and to be ready to respond.
Click here for the MAX32664 User Guide

Known Issues