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by dave j
Tue Nov 10, 2020 9:54 am
Forum: General discussion
Topic: Reason of KiCad nightly version necessity for CM4-IO board
Replies: 5
Views: 261

Re: Reason of KiCad nightly version necessity for CM4-IO board

There was a new version of KiCad release a few days ago. If that has the required features it's probably better to start advising people to use that rather than keep recommending nightly builds.
by dave j
Fri Jun 05, 2020 7:43 pm
Forum: Graphics programming
Topic: RPi4 Poor OpenGL performance question
Replies: 24
Views: 2521

Re: RPi4 Poor OpenGL performance question

tombsar wrote:
Fri Jun 05, 2020 1:57 pm
Thanks for testing! I wonder what's wrong with my setup then... I'll try a fresh image and report back.
Have you got the composition manager enabled? If so, try disabling it (using raspi-config).
by dave j
Mon Apr 20, 2020 3:36 pm
Forum: C/C++
Topic: memcpy source image to framebuffer with alpha channel
Replies: 12
Views: 795

Re: memcpy source image to framebuffer with alpha channel

tttapa wrote:
Mon Apr 20, 2020 12:50 pm
You don't even need the addition, you can just multiply it by 0x8081 ≃ 257 << 7 instead of 257 and shift it 23 bits instead of 16:
Good spot. Sometimes you can be a bit too close to a problem to see an obvious optimisation. ;)
by dave j
Mon Apr 20, 2020 9:56 am
Forum: C/C++
Topic: memcpy source image to framebuffer with alpha channel
Replies: 12
Views: 795

Re: memcpy source image to framebuffer with alpha channel

Where components contains r/g/b in the top 16 bits with bgR/bgG/bgB in the bottom 16 bits and alphas has alpha in the top 16 bits with 1-alpha in the bottom 16 bits. This only helps for rgb565, but the code shown before was for rgb888. http://www.keil.com/support/man/docs/armasm/armasm_dom136128990...
by dave j
Sun Apr 19, 2020 8:25 pm
Forum: C/C++
Topic: memcpy source image to framebuffer with alpha channel
Replies: 12
Views: 795

Re: memcpy source image to framebuffer with alpha channel

I have not used assembler code since I was writing code for a Z80 and even then was not very good at it. I don't understand how to add asm code into a C program. Is there a good resource for this? I have books on assembler but they are all for x86 DOS (very old) Stick this somewhere in your code (i...
by dave j
Sat Apr 18, 2020 7:56 pm
Forum: C/C++
Topic: memcpy source image to framebuffer with alpha channel
Replies: 12
Views: 795

Re: memcpy source image to framebuffer with alpha channel

I understand what DMA is but not how to access it. All I keep finding is DMA and GPIO. Here is my pixel code void put_pixel_alpha(int x, int y, unsigned int colour) { int r = (colour >> 16) & 0xff; int g = (colour >> 8) & 0xff; int b = colour & 0xff; unsigned int pix_offset = x*4 + y * fix.line_len...
by dave j
Sat Feb 22, 2020 2:06 pm
Forum: General discussion
Topic: What is this RPI Z w CPU?
Replies: 3
Views: 302

Re: What is this RPI Z w CPU?

What you're looking at is the RAM, not the CPU. The Pi Zero uses package on package to place the RAM on top of the CPU. The RAM manufacturer used changes depending on price, availability, etc.
by dave j
Sat Sep 21, 2019 4:27 pm
Forum: Graphics programming
Topic: S3TC Compression in RP4?
Replies: 3
Views: 2004

Re: S3TC Compression in RP4?

VC4 doesn't support S3TC texture compression. It does support ETC1, although it doesn't look like jMonkeyEngine3 supports it. I don't know about VC6.
by dave j
Sat Jul 27, 2019 9:25 am
Forum: Python
Topic: seeking 2D graphics engine for Python
Replies: 10
Views: 1427

Re: seeking 2D graphics engine for Python

Now Raspbian supports X based OpenGL, it might be worth trying pyglet.
by dave j
Thu May 23, 2019 1:05 pm
Forum: General discussion
Topic: Rpi as a scan converter / scaler, possible?
Replies: 8
Views: 1674

Re: Rpi as a scan converter / scaler, possible?

Thanks, That's great but I was thinking if it support the RGBS or RGBHV basically if it would work with a rgb-scart output of a PAL 50Hz Megadrive console. I'm not a BBC Micro expert, it would anyway looks like they have the same RGB output standard (?). Also is it sold somewhere or the developer h...
by dave j
Thu May 23, 2019 12:58 pm
Forum: General discussion
Topic: Rpi as a scan converter / scaler, possible?
Replies: 8
Views: 1674

Re: Rpi as a scan converter / scaler, possible?

Novel, and quite clever. Do note that this is using the Pi in bare metal mode, so it's dedicated to that one task. It's also below SD in resolution (pixel clock of 12 or 16MHz). The 12 and 16MHz pixel clocks are what the BBC uses for its screen modes. The device samples at 96MHz. There are examples...
by dave j
Thu May 23, 2019 9:45 am
Forum: General discussion
Topic: Rpi as a scan converter / scaler, possible?
Replies: 8
Views: 1674

Re: Rpi as a scan converter / scaler, possible?

Someone on the stardot Acorn retro forum has produced something that uses a Pi zero and a small CPLD to convert BBC Micro RGB output to HDMI . More recent developments allow it to convert other formats up to VGA. It also does de-interlacing and/or scan lines. Particularly interesting for you is that...
by dave j
Sun May 19, 2019 7:09 pm
Forum: General discussion
Topic: Atmega328p + RPI : ICSP programming providing 3.3V
Replies: 6
Views: 973

Re: Atmega328p + RPI : ICSP programming providing 3.3V

Have your thought of programming the AVR using the Pi? Using this page: Using Raspberry Pi as an Arduino (AVR) programmer and information in the Arduino IDE's files I've been able to program Arduino clones that use ATmega32U4. (That page is a bit out of date - the current Raspbian avrdude is built w...
by dave j
Tue Mar 19, 2019 4:39 pm
Forum: Graphics programming
Topic: 128x160 tft display
Replies: 4
Views: 1572

Re: 128x160 tft display

You haven't mentioned/linked to the library you are using which might help people answer. First of all, check if the library you are using has the ability to control display layout - it might already and you won't need the following: If the display does use the ST7735 chip you can find the datasheet...
by dave j
Sun Jan 13, 2019 5:13 pm
Forum: HATs and other add-ons
Topic: Interface boards for Quadrature Encoders
Replies: 3
Views: 1240

Re: Interface boards for Quadrature Encoders

If you can't find anything else more suitable, you could consider using an STM32 microcontroller. These are available on a prototyping friendly board very cheaply as blue pills . Many of the timers in these chips have an encoder mode for counting the inputs from a rotary encoder so you could use the...
by dave j
Sun Dec 02, 2018 7:50 pm
Forum: Off topic discussion
Topic: Complete ARM only Instruction Set (as promissed).
Replies: 36
Views: 6133

Re: Complete ARM only Instruction Set (as promissed).

jahboater wrote:
Sun Dec 02, 2018 6:12 pm
There is no portability issue at all using thumb2 since no source code changes are required. It is simply adding the one compiler flag: -mthumb.
Brilliant!
I was thinking of binary portability so you can have a single set of binaries that run on all Pis - same as Raspbian.
by dave j
Sun Dec 02, 2018 5:30 pm
Forum: Off topic discussion
Topic: Complete ARM only Instruction Set (as promissed).
Replies: 36
Views: 6133

Re: Complete ARM only Instruction Set (as promissed).

I think that if GCC can generate it then it should be in the list. After all, they are the instructions actually being used by our software. If I understand correctly GCC will generate also thumb instructions where appropriate. I have not been able to verify this. GCC can generate thumb instruction...
by dave j
Wed Nov 28, 2018 2:51 pm
Forum: Off topic discussion
Topic: Putting the RPi in the perspective, looking Retro.
Replies: 38
Views: 5701

Re: Putting the RPi in the perspective, looking Retro.

Copper: Only the Amiga had a Copper. Today the same thing can be done on the RPi with ease, though differently. This requires a small amount of code on the GPU, though within our limits, to implement the equivalent of a display list, and tell the DMA what to do. Though we only have one horizontal a...
by dave j
Tue Nov 20, 2018 3:46 pm
Forum: General discussion
Topic: Hexdump outputting too many radixes (was) VERY ANNOYING!!! [Solved]
Replies: 9
Views: 840

Re: Hexdump outputting too many radixes VERY ANNOYING!!!

You're much better off saving your BMP file in a format that doesn't have a header (or at least a fixed size one so you can discard the data you don't want). That 16 x 777 radixes is a) because it includes the BMP header, b) because you've got a 24 bit per pixel BMP file rather than a 16 bit one nee...
by dave j
Mon Nov 12, 2018 2:10 pm
Forum: HATs and other add-ons
Topic: TV HAT, missing EPG info.
Replies: 1
Views: 1141

Re: TV HAT, missing EPG info.

Just as an addendum to this. I found that the EPGs for some of the channels didn't update straight away. They did update overnight though so if you've done what itsmedoofer suggests and you still haven't got all the EPG info, try waiting a bit.
by dave j
Sun Nov 04, 2018 8:21 pm
Forum: General discussion
Topic: Does not start app on Raspberry Zero cross-compiled in Linux 64
Replies: 7
Views: 913

Re: Does not start app on Raspberry Zero cross-compiled in Linux 64

This bit in your ./configure command -device linux-rpi3-g++ looks like it's specifying compile for Pi3. You need to find what the value should be for Pi0. The reason the code works when compiled on your Pi3 it that Raspbian is configured to compile code that is compatible with all Pi versions. You n...
by dave j
Mon Oct 22, 2018 6:40 pm
Forum: Off topic discussion
Topic: Add Analog to Digital pins to the pi
Replies: 21
Views: 5929

Re: Add Analog to Digital pins to the pi

Just saying "add analog inputs to the Pi" is too vague to be meaningful. What resolution? What sample rate? How much jitter of sample times is acceptable (one built into the Pi is going to be fighting other circuitry for access to the memory bus)? How many channels? How many simultaneous channels? W...
by dave j
Fri Sep 07, 2018 7:12 pm
Forum: OpenGLES
Topic: Sliced front buffer rendering
Replies: 0
Views: 5645

Sliced front buffer rendering

Qualcomm and ARM GPUs have the ability to render to part of the front buffer without requiring loading and saving the rest of it - which is slow. (Qualcom have their QCOM_tiled_rendering extension and ARM uses scissor boxes.) It also looks like the Eric Anholt's driver supports it using scissoring ....
by dave j
Mon Jan 22, 2018 4:23 pm
Forum: General discussion
Topic: Arcade Monitor - Rotated display NOW Jumpy Graphics
Replies: 2
Views: 611

Re: Arcade Monitor - Rotated display NOW Jumpy Graphics

This is a known issue. Get your emulator to do the rotation rather than the config.txt entry.
by dave j
Wed Nov 15, 2017 11:52 am
Forum: C/C++
Topic: Help with ILI9225 display
Replies: 4
Views: 2664

Re: Help with ILI9225 display

First of all, if you haven't proved your software SPI implementation works by writing to a known working SPI implementation (e.g. one on your Arduino) ensure that it does - trying to debug two things at once needlessly complicates things. As to your screen code. Your drawPixel function defines a win...

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