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Trying to understand this center of mass methodology?

BigG — Mon, 31 Oct 2022 11:37:27 GMT

I am working through the Firmware Framework code and I came across this routine for center of mass calculation, which did not make sense at first glance.

I can't find anything online to confirm that this is the correct or maybe best approach. I did find this on stackoverflow but it's not really helpful in confirming if code methodology correct: https://stackoverflow.com/questions/66175912/center-of-mass-algorithm

void calcCenterOfMass(const int pixels[], const unsigned int xres, const unsigned int yres, float *cmx, float *cmy, int *totalmass)
{
int cmx_numer=0, cmy_numer=0;
for (unsigned int i = 0; i < xres*yres; i++) {
    cmx_numer += (i%xres)*pixels[i];
    cmy_numer += (i/xres)*pixels[i];
    *totalmass += pixels[i];
}
if (*totalmass == 0) {
    *totalmass = 1; // avoid NaN
}
*cmx = (float)cmx_numer/(float)(*totalmass);
*cmy = (float)cmy_numer/(float)(*totalmass);
}

For example, when calculating cmx_numer and cmy_numer, one uses modulus of xres and the other divides by xres. Struggling to work out if correct.

I'm also wondering about the "for" routine too.

So I am seeking feedback.

Does the runGesture function inside gesture.c make sense to you?

BigG — Sun, 16 Oct 2022 11:47:08 GMT

I am reviewing the Firmware Framework code to see where I need to make changes for my own application and I came across this code inside gesture.c which does not make sense to me...

void runGesture(int pixels[], GestureResult *gesResult)
{
  // Initialize result structure
  memset(gesResult, 0, sizeof(GestureResult));
  gesResult->state = STATE_INACTIVE;
  gesResult->gesture = GEST_NONE;

  // Noise filter
  if (gestCfg.enable_window_filter) {
    noiseWindow3Filter(pixels, gestCfg.window_filter_alpha, reset_flag);
  }

  // Process pixels for dynamic gesture
  if (1) {
    DynamicGestureResult dynamicResult;
    runDynamicGesture(&gestCfg, pixels, &dynamicResult);
    gesResult->state = dynamicResult.state;
    gesResult->n_sample = dynamicResult.n_sample;
    gesResult->maxpixel = dynamicResult.maxpixel;
    gesResult->x = dynamicResult.x;
    gesResult->y = dynamicResult.y;
  }
  // Process pixels for tracking
  if (0) {
    TrackingResult trackResult;
    runTracking(&gestCfg.trackingConfig, pixels, &trackResult);
    gesResult->state = trackResult.state;
    gesResult->maxpixel = trackResult.maxpixel; // Will override dynamic result if any
    gesResult->x = trackResult.x; // Will override dynamic result if any
    gesResult->y = trackResult.y; // Will override dynamic result if any
  }
}

How do these conditions get met...

// Process pixels for dynamic gesture
if (1) { ..... }

// Process pixels for tracking
if (0) { ..... }

Now wondering what it should read... any idea?

Establishing serial communication over UART instead of USB in MAX25405 EVKIT

rsjawale24 — Sun, 09 Oct 2022 15:18:55 GMT

The MAX25405EVKIT comes with a MAX32620FTHR board which is preprogrammed with custom binary file for the gesture recognition. The application note at Maxim Gesture Sensor EVKit Serial API (maximintegrated.com)

mentions "The serial interface can be implemented over the Universal Serial Bus (USB) virtual serial port or over a Universal Asynchronous Receiver-Transmitter (UART). The EV kit is shipped configured to use the USB serial port to work with the EV kit PC Graphical user Interface (GUI). If a UART serial interface is desired, custom firmware in binary format is available."

Upon researching more, I found the firmware_framework code that contains the code for gesture recognition compiled using mbed compiler.

The readme file says that a file called interface.h and interface.c define the communication protocol. When I open the interface.c file, I can see a comment in the code that says Option to implement serial API over UART instead of USB but there is only a MACRO set as #define macro_name 0

I tried to change the 0 to 1 and compile the code, however, it does not compile successfully. The USBDevice library shows some error while compiling.

Did anyone try to change the serial API over UART instead of USB? Was it successful?

EDIT: I have successfully compiled the code for UART. However, I'll do some experiments and write introductory blogs before I re-program the MAX32620FTHR board with my firmware.

3D printed stand for gesture sensor PCB

rsjawale24 — Wed, 05 Oct 2022 16:08:50 GMT

I was looking for a suitable stand to hold the MAX25405EVKIT PCB as shown in the picture on the main contest page.

While I was going through the documentation on Maxim's website, I found that they have provided the stl file for the stand so I decided to use the same and 3D print the support structure. Available for download here: MAX25405 IR Gesture Sensor with Lens for Automotive Applications | Maxim Integrated

Upon opening the stl file in slicing software (I use Ultimaker Cura) this is how it looked

My smart brain tried to rotate the model 90 degrees to the left and then use support structures to print it however, it failed. The layers being all horizontal and the long arm also being horizontal resulted in a weak structure and it broke easily while I was removing the support structure. Lesson learned, print it the way it was provided by Maxim.

This is the orientation I tried to print it in.

I was successful in printing it but...

While removing the support structure the stand broke apart in two pieces. It was very weak and easily breakable. Hence, I decided to reprint it in the same orientation as given by Maxim.

Here is the sliced stl with support structure. The default setting in Cura has a 45 degree angle for supports. Upon slicing with 45deg. support it does not cover the entire structure, so I lowered the angle to 40 deg.

I have used white PLA+ for printing the stand.

Here are my settings for the 3D printer -

Temp. 200 deg C

Layer height 0.2mm

Other setting default except for the support angle

This is at 45 deg. support. Notice the empty part in between

This is at 40 deg support angle

It took me about an hour and 20 mins to print this and the results were much better than my previous print. I could easily break the support structure without breaking the actual stand and it was quite sturdy as compared to previous one.

The stand with support removed -

The stand already has a hole for mounting the PCB.

I used two small screws to mount the PCB onto the stands.

Here's the PCB mounted on the 3D printed stand -

Received the kit for experimenting with gesture sensors

rsjawale24 — Mon, 03 Oct 2022 15:54:30 GMT

I received the kit for the experimenting with gesture sensors contest today. Thank you to the entire e14 team and Maxim Integrated (now ADI) for sponsoring the kit and for the swift delivery of the kit.

Here are some unboxing pictures, my first observations and comments on the kit.

The box came intact with no impacts/folds/cuts.

Inside the box was packing material for safety.

Upon further unboxing, another box was found inside.

This box contained three anti-static bags with different circuit boards (discussed later) and one more small box.

The box contains three bags -

1) MAX32620FTHR - evaluation board for the MAX32620 Arm^® Cortex^®-M4 microcontroller which was previously used in an e14 roadtest

(+) MAX31889EVSYS# Temperature Sensor Eval Board - Review - element14 Community and (+) MAX31889EVSYS# Temperature Sensor Eval Board - Review - element14 Community

The header pins were already soldered to the MCU PCB and were protruding through the anti-static bag. However, no visible damage to the headers is seen.

2) The MAX25105FSHLD - A shield for the eval board and to connect the gesture sensor. The shield has a DC jack for connecting power adapter and comes with female headers so that it can be plugged onto the MAX32620FTHR Board. It also has two connectors with a fine pitch which is used to connect the gesture sensor board with the shield.

3) The third bag contains the MAX25405EVKIT - for the MAX25405 optical IR sensor for gesture sensing. The width of the gesture sensor PCB is quite small around 9.4mm. On the top side of the PCB there are four IR emitters mounted on the PCB with provision to mount 5 more IR transmitters. In the centre of the PCB is a IR sensor array.

As quoted from the EVKIT weblink - "The application circuit operates by illuminating the user’s hand with a precision-controlled IR light source and measuring the reflected signal with the MAX25405’s 6x10 (60 pixel) IR sensor array. The four-LED IR light source is PWM controlled with external FETs from the MAX25405’s onboard FET driver. The return signal is analyzed with an embedded microcontroller that interprets the gestures."

Upon first observation, I noticed that the PCB is slightly bent (curved), which is natural given the PCBs length to width ratio and with components mounted on both sides of the PCB.

On the bottom side of the PCB, a similar connector is found which can be connected to the shield with the help of a suitable cable.

Unfortunately, no cable is provided in the contest kit so it will have to be purchased separately in order to move ahead with the project.

Lastly, the small box contains a power adapter for powering up the MCU board and the entire kit. The power adapter has a 3.3V and 2A output DC output to power the kit. However, the adapter input is US type. I have modular power sockets at home so this should work fine for me. If you don't have this type of power sockets, I would suggest using a 3.3V source from a power supply. As 3.3V power adapters are not so common. At least for me this is my first adapter with a 3.3V output.

I will soon start experimenting with the kit as soon as I get the connector cable. I will head out to my local electronics market to buy the connector cables for the boards.

Can't wait to experiment with the kit and see what other challengers build 🙂

Again, thanks to the e14 team and Maxim Integrated for coming up with this interesting contest and sponsoring the kit! 😃

If you have a question about the Experimenting with Gesture Sensors competition, kit or anything else, you can also ask it here.

rscasny — Wed, 07 Sep 2022 15:58:05 GMT

If you have a question about the Experimenting with Gesture Sensors competition, kit or anything else, you can also ask it here.