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by experix
Mon Feb 15, 2016 5:14 pm
Forum: Automation, sensing and robotics
Topic: Vehicle speed and license plate monitoring
Replies: 24
Views: 14231

Re: Vehicle speed and license plate monitoring

I hate to add complexity to your idea. but you will find a valuable market if you design the system to block license plate from being captured at the same time. This will increase your customer base 200 fold. That is how they do it here, sell cops detectors, and sell drivers detector detectors. I a...
by experix
Thu Feb 11, 2016 4:31 pm
Forum: Off topic discussion
Topic: PI "obsoletion-resistant"?
Replies: 21
Views: 2658

Re: PI "obsoletion-resistant"?

There are definitely issues that impede the learning: lack of diagrams for some of the hardware unavailability of source code and interface info on the GPU lack of descriptions for functions and ioctls in the drivers and on and on That said, I have not seen anything that gives you a more well-rounde...
by experix
Mon Feb 08, 2016 5:45 pm
Forum: General discussion
Topic: Disposable Pi Project ideas
Replies: 5
Views: 850

Re: Disposable Pi Project ideas

What can be learned from a fossilized Pi? I'm thinking, flood it with mud, compress it slowly until it all turns into a rock, and then see if you can detect the Pi in there by ultrasound or X-rays or something.
by experix
Sat Feb 06, 2016 6:03 pm
Forum: Astro Pi
Topic: general reference for sense-hat programming
Replies: 5
Views: 2030

Re: general reference for sense-hat programming

Is i2c enabled and sense-hat installed? If you install i2c-tools, what does i2cdetect -y 1 say? Thanks! indeed, i2c-tools was not installed. Maybe it ought to be part of the default installation, or at least noted in the sense-hat documentation. Also RTIMULibDrive11 needs 'sudo'. I strace'd RTIMULi...
by experix
Sat Feb 06, 2016 5:19 pm
Forum: Automation, sensing and robotics
Topic: A method to estimate external battery voltage
Replies: 8
Views: 1297

Re: A method to estimate external battery voltage

This looks like more trouble than using an ADC. And with a 8-input ADC you could (depending on battery design) probably monitor all of the intermediate voltages in a stack of cells and/or the separate stacks in a parallel arrangement, to get a much more detailed view of battery health.
by experix
Fri Feb 05, 2016 9:46 pm
Forum: Astro Pi
Topic: general reference for sense-hat programming
Replies: 5
Views: 2030

Re: general reference for sense-hat programming

I tried to run RTIMULibDrive11 as described in the link you gave me. It does this: Settings file not found. Using defaults and creating settings file Failed to open settings file for saveFailed to open I2C bus 1 Failed to open SPI bus 0, select 0 Failed to open SPI bus 0, select 1 No IMU detected Us...
by experix
Wed Feb 03, 2016 4:10 pm
Forum: General discussion
Topic: how to set date and time
Replies: 27
Views: 357203

Re: how to set date and time

jbowler wrote: To make it worse I believe recent builds of Linux 3.17 have a bug on the B (at least) which cause time drift, maybe a few seconds in 24 hours.
John Bowler
is that affected by overclocking?
by experix
Tue Feb 02, 2016 8:46 pm
Forum: Astro Pi
Topic: general reference for sense-hat programming
Replies: 5
Views: 2030

general reference for sense-hat programming

bump update: Feb 26 2016 I have made the second post relative to this. I has a LED framebuffer demo, a demo that reads /dev/input/event files (including the joystick), and a demo that explores temperature measurement via the three devices on sense-hat and the /sys file. Also, annotated header files ...
by experix
Tue Feb 02, 2016 7:38 pm
Forum: General programming discussion
Topic: Serial Port programming
Replies: 6
Views: 1200

Re: Serial Port programming

You seem to be worrying about the hardware, whether it is correctly transmitting the bytes that your program sends to the UART. If that is the case, something like what you say would be the way to go. If you want to verify the program's output, you could accompany each UART data write with a store-d...
by experix
Sat Jan 30, 2016 5:33 pm
Forum: Astro Pi
Topic: LED dead codes
Replies: 1
Views: 773

LED dead codes

I wrote a C program that exercises the LED matrix. Results: Writing values 0x0006 to 0x001f into the framebuffer makes blue lights come on, with increasing intensity. Likewise, (0x000c to 0x003f)<<5 makes green light, and (0x0006 to 0x001f)<<11 makes red light, and OR'ing any of these together makes...
by experix
Tue Jan 26, 2016 5:03 pm
Forum: Automation, sensing and robotics
Topic: variable ac motor driver
Replies: 9
Views: 3238

Re: variable ac motor driver

An AC motor is built for current reversing its direction every 1/120 of a second (or whatever frequency it is made for). That is not at all the same as PWM, but a H-bridge connected to PWM output does give you control over current direction, so maybe you can do that. It might need a lot of experimen...
by experix
Tue Jan 26, 2016 4:47 pm
Forum: General discussion
Topic: Unusual CPU Temperature
Replies: 13
Views: 1888

Re: Unusual CPU Temperature

If it is networked, do you see unusual network activity at that time?
by experix
Sat Jan 23, 2016 7:24 pm
Forum: Astro Pi
Topic: extend camera cable slot on sense hat
Replies: 1
Views: 880

extend camera cable slot on sense hat

For convenience in removing the sense hat, would it be safe to extend that camera-cable slot over to the board edge? Then I wouldn't need to unplug and re-attach the camera, which is a bit of a delicate operation.
by experix
Sat Jan 23, 2016 5:10 pm
Forum: Off topic discussion
Topic: An Energy Challenge 2016 (not really on topic)
Replies: 3
Views: 649

Re: An Energy Challenge 2016 (not really on topic)

If I am to judge the contest (which I am most emphatically not) I cannot award the prize to Heater because he has not 'recovered' the energy; he as merely observed it. To recover the energy, to me, means using it do do some work. Maybe the contest needs more clear rules, but they must be careful not...
by experix
Sat Jan 23, 2016 4:51 pm
Forum: Advanced users
Topic: [Need Help] Raspberry pi Ambient Light
Replies: 2
Views: 509

Re: [Need Help] Raspberry pi Ambient Light

Do you mean that the display devices should have their brightness and maybe color adjusted according to the ambient light? Maybe you could use photodiodes with color filters (and of course appropriate amplifiers and ADC) to measure the light. Or get an image from the camera, convert to bitmap format...
by experix
Thu Jan 21, 2016 4:59 pm
Forum: C/C++
Topic: Can I make this program into a library? Or am I better off??
Replies: 6
Views: 891

Re: Can I make this program into a library? Or am I better o

exe code in included files is a useful technique and there's nothing wrong with having it run in multiple processes simultaneously as long as there are no conflicts over resources such as files, GPIO, etc. If it's a re-entrant function not using such resources, no problem. It can even use static var...
by experix
Wed Jan 20, 2016 5:15 pm
Forum: C/C++
Topic: Can I make this program into a library? Or am I better off??
Replies: 6
Views: 891

Re: Can I make this program into a library? Or am I better o

The best, and maybe only, reason to make a library is that you might have multiple programs or processes using the same functions. Then the library saves you the trouble of duplicating code in different programs, which uses more memory and creates more opportunities for bugs to creep in through fail...
by experix
Wed Jan 20, 2016 5:01 pm
Forum: General discussion
Topic: Block size & lots of small files
Replies: 20
Views: 6109

Re: Block size & lots of small files

Maybe it is better to use a USB stick or hard drive, with filesystem constructed in the best way for lots of little files. Putting them there will save wear on your SD card and make the files much easier to archive and access from another machine, by moving the drive there, should you want to do that.
by experix
Mon Jan 18, 2016 4:38 pm
Forum: Astro Pi
Topic: Astro Pi Temperature Sensor Reading
Replies: 63
Views: 42232

Re: Astro Pi Temperature Sensor Reading

The heat pipe would keep the sensor temperature much closer to the temperature at the other end of the pipe, minimizing the effect of warm components near the sensor. It's the same principle as the heat pipe you find attached to the CPU in a laptop, except that one is about removing heat produced by...
by experix
Mon Jan 18, 2016 4:29 pm
Forum: Advanced users
Topic: Precise pulse counter
Replies: 21
Views: 6263

Re: Precise pulse counter

It's too bad the peripheral section doesn't seem to have a pulse counter. But it shouldn't be hard to find or design something you can use for that. It would be much more accurate and reliable than trying to service an interrupt on each pulse.
by experix
Mon Jan 18, 2016 4:21 pm
Forum: General discussion
Topic: Battery capacity calculations - Have I got this right?
Replies: 13
Views: 1818

Re: Battery capacity calculations - Have I got this right?

This is slightly off-topic, but when (not 'if') the battery starts to under-perform, it is possible/feasible to find out which cell has gone bad and replace it? Or should one assume they are all getting too old? I thought about this after somebody showed me his electrified bicycle with heavy and pro...
by experix
Sun Jan 17, 2016 7:14 pm
Forum: Astro Pi
Topic: Astro Pi Temperature Sensor Reading
Replies: 63
Views: 42232

Re: Astro Pi Temperature Sensor Reading

Could it be improved by attaching a good heat conductor or heat pipe to the sensor?
by experix
Fri Jan 15, 2016 3:52 pm
Forum: C/C++
Topic: 4 digits 7 segments display problem(dynamic lighting)
Replies: 4
Views: 1902

Re: 4 digits 7 segments display problem(dynamic lighting)

You have a loop with usleep calls in it. That's an OS call, meaning process suspension and all that. You can't get the kind of tight timing that you want, doing it like that. How about using a PWM output to control the brightness?
by experix
Fri Jan 15, 2016 3:31 pm
Forum: Advanced users
Topic: PI Super Computer Project
Replies: 12
Views: 1830

Re: PI Super Computer Project

The Pi isn't suitable for constructing a supercomputer in the sense of a collection of closely linked CPUs, but how about making a 'supercomputer' for problems designed to run over a network? I'm thinking SETI, protein folding, prime number searching and other endeavors where each node gets a proble...
by experix
Wed Jan 13, 2016 4:34 pm
Forum: C/C++
Topic: Hardware PWM programming?
Replies: 17
Views: 6400

Re: Hardware PWM programming?

In case you are talking about PWM via a serial-port connected device such as the Gertbot, that can be speeded up about 7-fold by doing all the serial-port manipulations in user-space rather than by read and write calls on the /dev file. I can send you info if you want to try it.

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