Raspberry Pi Forums

Daniel Gessel

Possibly get some negative values because you are not accounting for seconds part of the tv struct here: time_difference = (gettime_now.tv_nsec - start_time) / 1000; You need to add tv_sec delta * 1,000,000 to get a proper micro second delta. For timing, I use: u64 nanoseconds() { struct timespec ts...

Daniel Gessel

I thought I checked for R, C being ints in the posted code (didn’t see them defined) and OP stated they were doubles. I must not be seeing the code you found wher R & C are defined. My bad.

Daniel Gessel

Try casting time_difference to double before negating. Probably, negating an unsigned produces an unsigned (which is positive - likely the two’s compliment of the original value) and then converted to a double for the division.

Using unsigned values with math requires extra care... It’s often a pain.

Daniel Gessel

Congratulations! This is amazing work!

Daniel Gessel

I’m going slightly off topic since the OP asked about Windows, but cosider installing a Linux distro (Raspbian itself is an option) on your desktop for increased compatibility while getting your desktop’s performance for development (I don’t find compile times an issue, but everybody has their own p...

Daniel Gessel

Then you probably need a -I<path> option on your gcc command line. Do you know where the QHostinfo file is on your system? The path to that directory is what you’d use with the -I option.

Daniel Gessel

Does #include<QHostinfo.h> (instead of #include<QHostinfo>) help?

Daniel Gessel

I just started looking at the datasheet for the 9 dof IMU sensor on the hat and found out there is a temperature sensor provided because the magnetometer is temperature dependent. Not sure yet if the official code tries to take this into account or not - I just started playing with the hat and diggi...

Daniel Gessel

Any thoughts on the read/write sequence to replace the ioctl that reads a single 8 bit register? I haven’t tried to solve this with any device yet - seems like it would require more kernel calls; I’ve just been working with C and/or python examples to figure out how to make my own C device interface...

Daniel Gessel

I haven't worked out how to read registers in block mode, but I've gotten significant speedups updating the framebuffer in an SSD1306 (found in Adafruit's PiOled) by rolling my own I2C_SMBUS_I2C_BLOCK_DATA call to ioctl. Then I got a little more switching to plain old "write" - which let me update i...

Daniel Gessel

Thanks - I should’ve found that myself! But looks super helpful!

Daniel Gessel

OpenGL ES from the console is well supported, but the examples I’ve seen so far don’t use a mouse. Anybody have any tips? Thanks!

Daniel Gessel

So there are two PWM channels that are brought out to up to 4 pins. Then there’s using the dma engine, If I understand correctly, which can work for all GPIO pins. Finally, there’s SW PWM, which can be implemented with busy loops, real time clock checks, even Nano sleeps if you can live with variabi...

Daniel Gessel

I could only find 3 pwm pins on https://pinout.xyz, two of which are labeled PWM0. Is there a more complete, if less pretty and easy to read, reference - short of going to schematics?

Daniel Gessel

I don’t have answers, but I’m also interested in OpenCV. Can you do what you want with 2.4.9? Please keep updating us here on how it goes!

Daniel Gessel

You want something like a stack of these:
https://www.adafruit.com/product/2327
Or these:
https://www.dexterindustries.com/shop/pivotpi-board/
But for steppers, not servos, right?

These use I2C to control multiple servos....

Daniel Gessel

Thanks for the feedback! Some more web surfing led me to:

https://www.dexterindustries.com/shop/p ... pberry-pi/

Which I think is going to be a great starter kit for my little project.

Daniel Gessel

I’d like a Pi robotics kit for smaller Lego Technic sets (turning e.g. vehicles into rovers); there are at least a couple of Pi kits that will work with the Pi 3, but I found nothing going for small and light weight like I think could be done with a Pi Zero W. It seems I have to build it myself! I’m...

Daniel Gessel

Hi,

I just picked up a toy programming language project I had put down a while ago and am working to make it useful (or at least interesting) for Raspberry Pi enthusiasts of all ages.

Dan

Daniel Gessel

As far as I could find out, the rpi3 cpu runs at 500 MHz, has 4 cores and arm Neon instructions are 128-bit wide. Theoretical flops would than be 500*4*4 = 8 GFlops for the cpu, versus 24 GFlops for the GPU. Beautiful; thanks! I believe the rpi3 is closer to 1 GHz, however, making it 16 GFlops for ...

Daniel Gessel

Awesome work! What’s the reason for pocl’s poor fp performance? Does the CPU emulate floating point? Do you know the theoretical limits for GPU CPU in terms of straight instruction throughput?

Search found 121 matches

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Re: negative number in C++ code is giving problems

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