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by mrmsbarnes
Mon Jul 16, 2018 5:44 am
Forum: Troubleshooting
Topic: Edited fstab, rebooted, Cannot access to console, the root account is locked
Replies: 12
Views: 28074

Re: Edited fstab, rebooted, Cannot access to console, the root account is locked

What is amazing is that when you hit Enter, the operating system is capable of fixing the lock and continuing with boot up. Which says the Raspbian people really don't want you running their OS unattended. They don't give a flying about headless. No, they want you right there in attendance for every...
by mrmsbarnes
Tue May 15, 2018 10:47 pm
Forum: OpenGLES
Topic: getting a square-pixels pi3d Display
Replies: 3
Views: 6031

Re: getting a square-pixels pi3d Display

My question stands, but I did find out no anisometric display on a normal HDMI monitor of 1920 x 1080 pixels. On my Asus monitor of 1920 x 1200, the stretching is very noticeable. Something in pi3d believes a monitor width of 1920 means 1080 units of height. I'll try to contact the author.
by mrmsbarnes
Tue May 15, 2018 5:50 pm
Forum: OpenGLES
Topic: getting a square-pixels pi3d Display
Replies: 3
Views: 6031

getting a square-pixels pi3d Display

Nothing I can think to do corrects the anisotropy I see in my full screen display. Spheres look more like eggs. Any ideas where in the openGL or pi3d code this can be fixed?
by mrmsbarnes
Thu Dec 07, 2017 10:45 am
Forum: Python
Topic: python scripts won't run
Replies: 10
Views: 1471

Re: python scripts won't run

Just wanted to say Thank You. Your posts are completely intelligible and helped me save more than the time it took you. :)
by mrmsbarnes
Mon Jun 26, 2017 5:52 pm
Forum: Troubleshooting
Topic: PiCam Status
Replies: 3
Views: 1096

Re: PiCam Status

You are not an amateur. This may be late but one way to handle your case is demonstrated by this short script from picamera import PiCamera import sys try: camera = PiCamera() print 'handle normal, non-exceptional case' except: print 'handle exceptional case' finally: print 'join up. On with the sho...
by mrmsbarnes
Tue Sep 09, 2014 8:32 pm
Forum: Advanced users
Topic: Accurate timing for real time control
Replies: 27
Views: 51351

Returning to the scene of the crime.

I found pi-blaster was overkill for what I was looking for (accurate clock). I just wanted to post this link: http://panteltje.com/pub/ If you search for freq_pi.c or freq_pi-0.2.c on the page, Jan Panteltje has provide a c-level gpio clock generator that works well and covers a large range of frequ...
by mrmsbarnes
Fri Aug 29, 2014 10:04 pm
Forum: C/C++
Topic: Alternative to SPI
Replies: 9
Views: 2926

Re: Alternative to SPI

examine assembly code - or do a comparative timing of a million SPI transfers. Which is what I should have done rather than speculate here. Good point though, Joan.
by mrmsbarnes
Fri Aug 29, 2014 5:56 pm
Forum: C/C++
Topic: Alternative to SPI
Replies: 9
Views: 2926

Re: Alternative to SPI

*(gpioReg + GPCLR0 + PI_BANK) = PI_BIT;
sounds pretty much like
{*gpioSet = pin17;}
to me. But the former has two additions and two macros evaluated from what I can see. My optimization was trying to cut down on the c code executed. I could still be wrong, but...
by mrmsbarnes
Fri Aug 29, 2014 1:18 am
Forum: C/C++
Topic: Alternative to SPI
Replies: 9
Views: 2926

Re: Alternative to SPI

In mmapGpio.h is see: void inline writePinHigh(unsigned int pinnum){*(this->gpio + GPFSET0) = (1 << pinnum);} void inline writePinLow(unsigned int pinnum){*(this->gpio + GPFCLR0) = (1 << pinnum);} which sounds real good and fast. I was wondering, if we were trying to achieve speed, perhaps at the ex...
by mrmsbarnes
Fri Aug 08, 2014 8:00 pm
Forum: Advanced users
Topic: Accurate timing for real time control
Replies: 27
Views: 51351

Re: Accurate timing for real time control

Now I believe gpioTick() from pigpio's minimal_gpio.c (thanks joan) is the hammer that hits all nails. #include <sys/fcntl.h> /* O_RDWR, O_SYNC */ #include <sys/mman.h> /* mmap and options */ #define SYST_BASE 0x20003000 #define SYST_LEN 0x1C #define SYST_CLO 1 static volatile uint32_t *syst_reg; vo...
by mrmsbarnes
Thu Aug 07, 2014 2:08 am
Forum: Raspbian
Topic: How to disable screen blanking
Replies: 42
Views: 252250

Re: How to disable screen blanking

About 2 years ago Rasadmin may well have posted THE answer for your system. However, I vote for carlhage, because that solution worked for my late model Raspbian system (uname -r says '3.12.22+' with LXDE display manager). Don't put magic xset commands in /etc/rc.local as advised elsewhere. Use the ...
by mrmsbarnes
Wed Aug 06, 2014 7:15 pm
Forum: Automation, sensing and robotics
Topic: Driving multiple servos from the RaspberryPi
Replies: 209
Views: 97943

Re: Driving multiple servos from the RaspberryPi

Richard, You have the power (should have the power) to modify your original post to note you no longer provide 'ready built' drivers at your git repository (unless I'm mistaken - still newish to git). That way newishbies won't read 8 pages of replies to be certain such was not already covered. OTOH,...
by mrmsbarnes
Sun Aug 03, 2014 12:39 am
Forum: Advanced users
Topic: Accurate timing for real time control
Replies: 27
Views: 51351

Re: Accurate timing for real time control

Regards the two samples I submitted. They were both run under X (I need my UI, man). In the second example callbacks are not involved. The loop only uses gpioTick and the gpioRead's and gpioWrite's. I believe joan is correct that the gpio reads and writes are susceptible to interrupts. That's the pr...
by mrmsbarnes
Fri Aug 01, 2014 10:48 pm
Forum: Advanced users
Topic: Accurate timing for real time control
Replies: 27
Views: 51351

Re: Accurate timing for real time control

Regrettably I cannot resurrect the exact code nor breadboard setup I was using. However, I can still provide two samples (if I can post code correctly) that show the problem I think petzval is trying to overcome. The first sample is a modification of joan's code. Instead of sleeping while the square...
by mrmsbarnes
Fri Aug 01, 2014 6:07 am
Forum: Advanced users
Topic: Accurate timing for real time control
Replies: 27
Views: 51351

Re: Accurate timing for real time control

The pigpio library is certainly a marvel and a huge convenience, and if you stick to gpioRead (no writes) you can even get nearly reliable accuracy (repeatable performance). If you use gpioWrite, however, in even a simple loop, not as in the fast loop in minimal_gpio.c, you will see a very different...

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