This page is next level of Virtual Touch Screen project. 

Do you have this impression, like video I posted earlier was outdated? Software to draw a handwriting, mouse interface, etc. Wouldn’t it be nice to use a new era  technology? And here it is.

Technically, there are two hardware parts were added, to fully demonstrate extra ordinary sensitivity of the VTS project. First one is the BlueTooth module. And second is a tablet, running android. Device that I have, doesn’t support USB host mode (OTG), otherwise I may be fine w/o BT, just transfer a data over USB cable, as it was done in two previous demo video clips.  Have to say, it was not easy to represent 3D perspective on a flat screen, and picture below shows what I designed to complete a task:

Don’t think it requires a comments, the tricky part was to create an elliptical grid to show a distance. The number of circles is not limited to 2, I’d think about how to film next demo video, that ‘d show a “volume”.

Enjoy the movie:

This page is next level of Virtual Touch Screen project. 

First things is a distance, for virtual touch screen its less than 3 m, because the reflective area is too small. For radar (or sonar) its different, and the bigger size of object the stronger echo. Approximated range of detection the object as big as a wall, 30 meters.

Technically, there are two hardware parts were added, to fully demonstrate extra ordinary sensitivity of the VTS project. First one is the BlueTooth module. And second is a tablet, running android. Device that I have, doesn’t support USB host mode (OTG), otherwise I may be fine w/o BT, just transfer a data over USB cable, as it was done in two previous demo video clips.  Have to say, it was not easy to represent 3D perspective on a flat screen, and picture below shows what I designed to complete a task:

Don’t think it requires a comments, the tricky part was to create an elliptical grid to show a distance. The number of circles is not limited to 2, I’d think about how to film next demo video, that ‘d show a “volume”.

Enjoy the movie:

There are two apples, and arduino measure position in 3D space both of them. X, Y, and Z coordinates plus P – power of reflected ultrasonic wave used to draw circles, with different colors. You can see movement of the red circle on screen when first apples moves.

edited on 21-08-2014

After thinking awhile how to show a “volume” on a flat tablet screen, I decide to remove filtering stage in a software, when a bunch of consecutive “layers” were shown as one single ring (object) on a screen. Now each packet of data received from single “spherical” layer creates a circle. As always packet includes X, Y, Z, and P. To make an image “clear” there are two others filters left over in the processing algorithm. One is rejecting data below ( selectable in a menu ) power threshold, and another rejects anything thats located farther specific (again, selectable) distance. This is why in a video you can see only a ball, but not me – operator making a movie.

Here is how the ball looks like on radar screen:

And video:

That;s it for now.

Internal Development of the Arduino TRE, Torino, Italy

Beta-testing program

More than 100 beta-testers are involved in the program, from a variety of backgrounds and ages. Most of the hardware tests have been completed by this incredible group of people. Beta-testers have been giving feedback on the software side too: as soon as we come up with a new release they try it out and report any issue they find. Beta-testers have also been helping out on porting existing examples to the TRE. Examples are really crucial to get beginners started with a new environment and this is even more relevant for this board, since it has so much more potential than classic Arduinos.

We are also very excited to see the results of the projects that are already in progress: a Robotic Arm, a Smart Thermostat, a DSLR Controller, a Car Diagnostic Dashboard, and a variety of audio/video projects.

Coming soon: Learn about the testing suite we are putting together to check all the production boards!

   First things: there are no servo motors. No motors or any mechanical moving parts in this project.

There are 4 HC-SR04 ultrasonic sensor units, only one is working as transmitting – pinging module and receiver simultaneously, 3 others are just receivers. Arduino DUE, of course, is a prime violin of the whole project. Small prototype board has an additional 4-channel buffer amplifier (MCP6024).

Technical specification ( approximately ):

• Scanning range 3 m, limited very low power and sensitivity of the HC-SR04 devices.
• Spacial XY resolution depends on a distance, has to be determined.  Two object should be position at least 5 cm apart and not on the same spherical surface around sensor board.
• Directivity diagram +-30 degree, or so.
• Spacial Z – (distance) resolution 12 um. No typo error, micrometers.
• Time to complete full scan 16 milliseconds, frame rate may vary from 60 Hz down to 10 Hz if there is strong reverberation.

Have to say, that ultrasonic units were slightly modified, to brought out an analog signal (40 kHz) before it gets quantization in the local uCPU.  After amplification, 4-channels are digitized by arduino’s ADC (12-bits 1 MSPS).

Fast Fourier Transform, not much differs from the published on this blog library. I’m not ready to disclose complete signal processing algorithm, and is not publishing a code, at this time. Nevertheless, I don’t mind to answer reasonable /meaningful questions.

Video: have to practice more -);

A few comments on a video clip. I intentionally use a pen to draw a picture, even it’s almost violate the basic of the physics, because reflective area of the pen practically equals to wave length, 8.5 mm for 40 kHz in the air. You can see, that arduino is loosing track on a few occasions. Distance ~ 1m.

Computer is running Linux with regular “mtPaint 3.40″ from official source. Software is receiving a mouse commands, as its has no idea where this commands come from. In the same way, if you draw a picture manually. To interface with a host, arduino emulates a left button and XY move mouse commands using “build-in” mouse driver, and I copy ButtonMouseControl example from IDE.

The surface of the touch screen is “virtual”, first things arduino does after I send a command over serial monitor console to start a drawing, is “search – scan” an object. Whatever it finds first, the closest one, would be “locked” and distance to this object is interpreted as “touched – non touched”. This is first try, and I was not pushing hard on the gesture pattern recognition yet. But as you can guess, there is no limits to “slide” “rotate” “scroll” etc movement discrimination, with only one exception. There is no “multi-touch”, as I mentioned in the specification section, two object has to be 5 cm apart. This limitation is introduced by two shortcomings of the current hardware design. First one, because there is no phase array, only one unit is transmitting ( in the middle on right side ), so there is no way arduino could identify two objects on the same sphere. Second, is low sampling rate of the ADC. In order to “shrink” XY spatial resolution down to wave length (8.5 mm), sampling rate has to be at least 6 MSPS or so.

Tracking update rate (scan frame rate – don’t confuse with a video)  is set to 32 fps.

Photo:

 eddited: 14 Aug. 2014       “New technology is rising!”

Second video clip is posted, that demonstrates better tracking stability over bigger distance range. 

First things: there are no servo motors. No motors or any mechanical moving parts in this project.

There are 4 HC-SR04 ultrasonic sensor units, only one is working as transmitting – pinging module and receiver simultaneously, 3 others are just receivers. Arduino DUE, of course, is a prime violin of the whole project. Small prototype board has an additional 4-channel buffer amplifier (MCP6024).

Technical specification ( approximately ):

• Scanning range 3 m, limited very low power and sensitivity of the HC-SR04 devices.
• Spacial XY resolution depends on a distance, has to be determined.  Two object should be position at least 5 cm apart and not on the same spherical surface around sensor board.
• Directivity diagram +-30 degree, or so.
• Spacial Z – (distance) resolution 12 um. No typo error, micrometers.
• Time to complete full scan 16 milliseconds, frame rate may vary from 60 Hz down to 10 Hz if there is strong reverberation.

Have to say, that ultrasonic units were slightly modified, to brought out an analog signal (40 kHz) before it gets quantization in the local uCPU.  After amplification, 4-channels are digitized by arduino’s ADC (12-bits 1 MSPS).

Fast Fourier Transform, not much differs from the published on this blog library. I’m not ready to disclose complete signal processing algorithm, and is not publishing a code, at this time. Nevertheless, I don’t mind to answer reasonable /meaningful questions.

Video: have to practice more -);

A few comments on a video clip. I intentionally use a pen to draw a picture, even it’s almost violate the basic of the physics, because reflective area of the pen practically equals to wave length, 8.5 mm for 40 kHz in the air. You can see, that arduino is loosing track on a few occasions. Distance ~ 1m.

Computer is running Linux with regular “mtPaint 3.40″ from official source. Software is receiving a mouse commands, as its has no idea where this commands come from. In the same way, if you draw a picture manually. To interface with a host, arduino emulates a left button and XY move mouse commands using “build-in” mouse driver, and I copy ButtonMouseControl example from IDE.

The surface of the touch screen is “virtual”, first things arduino does after I send a command over serial monitor console to start a drawing, is “search – scan” an object. Whatever it finds first, the closest one, would be “locked” and distance to this object is interpreted as “touched – untouched”. This is first try, and I was not pushing hard on the gesture pattern recognition yet. But as you can guess, there is no limits to “slide” “rotate” “scroll” etc movement discrimination, with only one exception. There is no “multi-touch”, as I mentioned in the specification section, two object has to be 5 cm apart. This limitation is introduced by two shortcomings of the current hardware design. First one, because there is no phase array, only one unit is transmitting ( in the middle on right side ), so there is no way arduino could identify two objects on the same sphere. Second, is low sampling rate of the ADC. In order to “shrink” XY spatial resolution down to wave length (8.5 mm), sampling rate has to be at least 6 MSPS or so.

Tracking update rate (scan frame rate – don’t confuse with a video)  is set to 32 fps.

Photo:

eddited: 14 Aug. 2014       “New technology is rising!”

Second video clip is posted, that demonstrates better tracking stability over bigger distance range.

Distance is 1.2 m, same pen. I think, that all for Virtual Touch Screen demonstration. Any improvements I could make in a code ‘d introduced only small changes in overall representativity of the project.

This HID technology is completely new area for me, and I’m not a professional programmer. Be curious, I look into “regular” touch screen (resistive – capacitive)  library free accessible on the i-net. I find over 100 variables that initialized and updated in order to keep track on a bunch of real-time parameters, that “normal” TS supplies with 10 ms time interval. Another 100′s variables are buried inside proprietary driver in the OS. It would takes a years to run a test and debug effects each of this variables on stability, smoothness,  susceptibility etc. And moreover, my invention Virtual TS – 3D would require a lot more than a 100′s….

edited: 26 Aug. 2014   Answering the question, modification to HC-SR04 module.

There is an electrical drawings, I was able to locate on-line:

http://uglyduck.ath.cx/HC-SR04E/HC-SR04E.svgz

And photo:                  

As you can see, analog 40 kHz output is taken from pin 7, LM324. Conveniently,  it’s the rightest one, close to the board edge. Module – transmitter has a jumper wire over B-E of the transistor, others 3 units may not have this wire. I find out, that unit doesn’t transmit anything till it gets a response, that may never happened for echo reflected from tiny object like a pen.  It looks like on-board uCPU is waiting a transition in poling mode.  And additional amplification stage I build with MCP6024, is similar to first stage of the LM324 (U2D), with a gain x50.  In my first try, I connect output of LM324 directly to arduino DUE analog inputs, basically its not realy safe, as voltage goes close to 3.6-3.7 V. But than introducing MCP6024 (rail-to-rail) I decrease power voltage of the OPA down to 3.3V,  not to worry about my DUE.

For the last couple of days I’ve been working on designing and building a PWM controller capable of handling moderately large currents at modest voltages (5A @ 9V). I don’t need high PWM frequency (4kHz should be plenty), but some of the loads I’m thinking of are rather nonlinear (very little current at low voltages, large but constant current at higher voltages).

I decided to try using an ATtiny chip as the PWM controller, because they are very cheap and can be programmed from the Arduino IDE (using an Arduino board as the ISP programmer).  I first prototyped the design using a Arduino ProMini (so I could add debugging statements and not have to worry about the 1kByte flash limitation of the ATtiny13A).  Once that was working, I rewrote the code for the ATtiny, doing some hand optimization to reduce the code size. I got it down to 880 bytes, but I can see why C is more popular than C++ for the really tiny processors—the C++ and Arduino overhead accounts for about 150 of the 1k bytes of flash!  I could make my code much smaller if I made it more special purpose and did everything in C rather than C++, but once it fit in the 1024 bytes, I stopped worrying about the size.

PWM controller using ATtiny 13A

The design I came up with uses a low-dropout regulator to provide 5V for the ATtiny13A. A potentiometer provides analog input and a nFET provides a low-resistance switch for the output. I used the AOI518, because I have some on hand, but they are reaching the “end of life” so some other nFET may need to be used in a future design (perhaps one of the others in the series, such as the AOI516 which has a slightly lower on-resistance but a slightly higher gate capacitance).

The capacitors C1 and C2 are to keep the switching of the large load from propagating spikes into power supply.  The 470µF capacitor with a 5A current spike should limit the voltage slew to 10.6V/ms—with a 4.7kHz current square wave, this would be about a 1.1V triangle wave.  A polymer electrolytic is used (despite the price) to keep the effective series resistance small.  The one I’m using has an ESR of 9mΩ (@100kHz) and a ripple current up to 6.1A.  The leakage current could be as high as 1.5mA though.  C1 is a small ceramic capacitor to remove higher-frequency noise.  The big Schottky diode on the input is just to provide protection against accidentally hooking the circuit up backwards. I should probably add a 60¢ resettable fuse as well, to keep the current from getting excessive if there is a short.

When there is no load, the maximum current draw is 1.9mA for the pullup resistor R2, 0.9mA for the pot, 4–6mA for the ATtiny13A, and up to 1.5mA for C2, for a total of 8.3–10.3mA.  With a typically 80% efficient 9v switching power supply, this is a waste of about 100mW, or about 0.9kWh/year.

The pullup resistor R2 is not strictly necessary, but was added to keep the PWM pulses clean, turning all the way off even when the load had only tiny current draw—otherwise I could not get very low duty-cycle pulses to work well—the nFET acted as if it were a 1.3nF capacitor and kept a low voltage even when the nFET was off.  With the 4.7kΩ pullup, the voltage goes up appropriately, with a time constant of about 6µs.

So far, I’ve not tried the circuit with a large load—just with a small load that takes 13mA.  With that tiny a load, I don’t see any ripple in the power supply from the PWM.  With a 210mA load, the ripple on the power supply is noticeable: on top of the 20mV of ripple at about 20MHz with no load, I see 30mV of ripple synchronized with the switching of the PWM, when switching 210mA with a duty cycle of 1/2.  Without the 470µF polymer capacitor, the synchronized ripple is more like 200mV, indicating that the capacitor is indeed smoothing out the ripple.

The 30mV swing on 210mA implies that I should see about a 710mV swing if switching 5A.   That shouldn’t cause a problem in my design, but I do need to allow a little more voltage so that the swing isn’t a problem.  I could also use a bigger capacitor, but the polymer electrolytics are a bit expensive, and the regular wet electrolytics can’t handle a big ripple current—one with the same 6A ripple current rating would be 20 times the volume and 3 times the price of the polymer capacitor.

The high-frequency noise is almost certainly coming from the ATtiny, as it is synchronized with the PWM signal. The 5V power supply at the ATtiny is showing a 40mV ripple, which is large considering that there is a bypass capacitor on the Vdd pin.  There is a lot of inductance from the wiring on the board though, which could be increasing the propagation of the high-frequency noise.

For the last couple of days I’ve been working on designing and building a PWM controller capable of handling moderately large currents at modest voltages (5A @ 9V). I don’t need high PWM frequency (4kHz should be plenty), but some of the loads I’m thinking of are rather nonlinear (very little current at low voltages, large but constant current at higher voltages).

I decided to try using an ATtiny chip as the PWM controller, because they are very cheap and can be programmed from the Arduino IDE (using an Arduino board as the ISP programmer).  I first prototyped the design using a Arduino ProMini (so I could add debugging statements and not have to worry about the 1kByte flash limitation of the ATtiny13A).  Once that was working, I rewrote the code for the ATtiny, doing some hand optimization to reduce the code size. I got it down to 880 bytes, but I can see why C is more popular than C++ for the really tiny processors—the C++ and Arduino overhead accounts for about 150 of the 1k bytes of flash!  I could make my code much smaller if I made it more special purpose and did everything in C rather than C++, but once it fit in the 1024 bytes, I stopped worrying about the size.

PWM controller using ATtiny 13A

The design I came up with uses a low-dropout regulator to provide 5V for the ATtiny13A. A potentiometer provides analog input and a nFET provides a low-resistance switch for the output. I used the AOI518, because I have some on hand, but they are reaching the “end of life” so some other nFET may need to be used in a future design (perhaps one of the others in the series, such as the AOI516 which has a slightly lower on-resistance but a slightly higher gate capacitance).

The capacitors C1 and C2 are to keep the switching of the large load from propagating spikes into power supply.  The 470µF capacitor with a 5A current spike should limit the voltage slew to 10.6V/ms—with a 4.7kHz current square wave, this would be about a 1.1V triangle wave.  A polymer electrolytic is used (despite the price) to keep the effective series resistance small.  The one I’m using has an ESR of 9mΩ (@100kHz) and a ripple current up to 6.1A.  The leakage current could be as high as 1.5mA though.  C1 is a small ceramic capacitor to remove higher-frequency noise.  The big Schottky diode on the input is just to provide protection against accidentally hooking the circuit up backwards. I should probably add a 60¢ resettable fuse as well, to keep the current from getting excessive if there is a short.

When there is no load, the maximum current draw is 1.9mA for the pullup resistor R2, 0.9mA for the pot, 4–6mA for the ATtiny13A, and up to 1.5mA for C2, for a total of 8.3–10.3mA.  With a typically 80% efficient 9v switching power supply, this is a waste of about 100mW, or about 0.9kWh/year.

The pullup resistor R2 is not strictly necessary, but was added to keep the PWM pulses clean, turning all the way off even when the load had only tiny current draw—otherwise I could not get very low duty-cycle pulses to work well—the nFET acted as if it were a 1.3nF capacitor and kept a low voltage even when the nFET was off.  With the 4.7kΩ pullup, the voltage goes up appropriately, with a time constant of about 6µs.

So far, I’ve not tried the circuit with a large load—just with a small load that takes 13mA.  With that tiny a load, I don’t see any ripple in the power supply from the PWM.  With a 210mA load, the ripple on the power supply is noticeable: on top of the 20mV of ripple at about 20MHz with no load, I see 30mV of ripple synchronized with the switching of the PWM, when switching 210mA with a duty cycle of 1/2.  Without the 470µF polymer capacitor, the synchronized ripple is more like 200mV, indicating that the capacitor is indeed smoothing out the ripple.

The 30mV swing on 210mA implies that I should see about a 710mV swing if switching 5A.   That shouldn’t cause a problem in my design, but I do need to allow a little more voltage so that the swing isn’t a problem.  I could also use a bigger capacitor, but the polymer electrolytics are a bit expensive, and the regular wet electrolytics can’t handle a big ripple current—one with the same 6A ripple current rating would be 20 times the volume and 3 times the price of the polymer capacitor.

The high-frequency noise is almost certainly coming from the ATtiny, as it is synchronized with the PWM signal. The 5V power supply at the ATtiny is showing a 40mV ripple, which is large considering that there is a bypass capacitor on the Vdd pin.  There is a lot of inductance from the wiring on the board though, which could be increasing the propagation of the high-frequency noise.

Tom Igoe some days ago wrote an interesting post about Arduino Yún on his blog.  We post it here as it could be useful to the Arduino Community.

————————–

Recently, Federico Fissore added node.js to the package repository for the Arduino Yún. Here’s how you get node to communicate with the Arduino processor on the Yún via the Bridge library.

To do this, you’ll need an Arduino Yún, a microSD card, a microUSB cable and a wifi connection. You should be familiar with the basics of the Arduino Yún and node.js in order to get the most out of this post.

All of the code for this post can be found on my GitHub repository.

First you’ll need to install node on the Yún. Make sure you’ve upgraded to the current Yún software image and have connected to the internet via wifi. Then ssh into your Yún, or connect to the command line interface using the the YunSerialTerminal sketch, and issue the following commands:


$ opkg update
$ opkg install node


That’s it. Now you have node.js onboard. You can check that it’s okay by checking the version:

$ node -v

You should get the version number in reply.

Once you’ve got that working, you’ll undoubtedly want to communicate with the Yún’s Arduino processor from node. You can do this using the Bridge library. On a microSD drive, make a directory for your node scripts. I called mine /arduino/node. Then insert it into your Yún. For reference, its path from the command line is /mnt/sda1/arduino/node.

Note: The Yún automatically treats the microSD card’s /arduino/www/ directory as a public web directory. Anything you put in there will be served out as static HTML. So you may not want to put your node scripts in this directory, so they’re not visible via the browser. That’s why I created a node directory at the same level as the www directory, but outside it.

Read the complete post at this link>>

My son finished the last of his college application essays today—a letter of intent for the College of Creative Studies at UCSB.  UCSB is more of a safety school for him than a first-choice one, but they have a decent CS department, and the College of Creative Studies is a better honors program than the other UC campuses have.  It looks like that program provides enough flexibility in the general ed requirements that he would have relatively few courses to take that he did not choose for himself—certainly less than the rather specific laundry lists of UCSD colleges or UCB.

I had to bicycle down to the post office to mail paper copies of the application forms to the College of Creative Studies, because my son was running late for his afternoon appointment, and the forms really needed to be postmarked today.  It seemed a bit weird and old-fashioned to be sticking stamps on a big envelope and mailing it from the post office for a college application.  Of course, the College of Creative Studies is small enough that they can’t really afford to set up their own on-line application system, and UC is not about to modify their system to accommodate a small college on one campus.

Now that he has finally finished his essays, I’m hoping to get him to spend some time on two subjects he’s been neglecting: group theory and updating the data logger to work with the Freescale processors (along with lots of other upgrades requested on the bitbucket site).  I’ll have to tell the lab staff soon which processors the students will be buying for the spring quarter Applied Circuits course.  If the data logger is not working with the KL25Z boards, then we’ll have to continue using the Arduinos.  The Arduinos worked well enough last year, but we could run much higher sampling rates and higher resolution on the KL25Z boards.  I’m also wondering whether I should get a KL26Z board, which has 14-bit resolution for 3-axis acceleration measurements and 16-bit resolution for 3-axis magnetic measurements (the KL25Z board has only 12-bit resolution for 3-axis acceleration and no magnetometer).  Both boards have 48MHz ARM Cortex M0+ processors with 28kB of flash and 16kB of RAM, and use similar OpenSDA interfaces for downloading programs. The KL25Z is supported by free software from mbed.org, but the KL26Z does not seem to be (yet—they do support the KL46Z).

My son finished the last of his college application essays today—a letter of intent for the College of Creative Studies at UCSB.  UCSB is more of a safety school for him than a first-choice one, but they have a decent CS department, and the College of Creative Studies is a better honors program than the other UC campuses have.  It looks like that program provides enough flexibility in the general ed requirements that he would have relatively few courses to take that he did not choose for himself—certainly less than the rather specific laundry lists of UCSD colleges or UCB.

I had to bicycle down to the post office to mail paper copies of the application forms to the College of Creative Studies, because my son was running late for his afternoon appointment, and the forms really needed to be postmarked today.  It seemed a bit weird and old-fashioned to be sticking stamps on a big envelope and mailing it from the post office for a college application.  Of course, the College of Creative Studies is small enough that they can’t really afford to set up their own on-line application system, and UC is not about to modify their system to accommodate a small college on one campus.

Now that he has finally finished his essays, I’m hoping to get him to spend some time on two subjects he’s been neglecting: group theory and updating the data logger to work with the Freescale processors (along with lots of other upgrades requested on the bitbucket site).  I’ll have to tell the lab staff soon which processors the students will be buying for the spring quarter Applied Circuits course.  If the data logger is not working with the KL25Z boards, then we’ll have to continue using the Arduinos.  The Arduinos worked well enough last year, but we could run much higher sampling rates and higher resolution on the KL25Z boards.  I’m also wondering whether I should get a KL26Z board, which has 14-bit resolution for 3-axis acceleration measurements and 16-bit resolution for 3-axis magnetic measurements (the KL25Z board has only 12-bit resolution for 3-axis acceleration and no magnetometer).  Both boards have 48MHz ARM Cortex M0+ processors with 28kB of flash and 16kB of RAM, and use similar OpenSDA interfaces for downloading programs. The KL25Z is supported by free software from mbed.org, but the KL26Z does not seem to be (yet—they do support the KL46Z).