Modifying code to add 640x400 monochome resolution with different scan freqencies

[jdelange]

Hi, if I want to update the code to allow for a new resolution of 640x400 with 45.5 Hz and 18.6 kHz frequencies (ATT400 / Olivetti monochrome), then what is the easiest way to do this? 1) Add a new profile mimicking the other profiles and adjust as required, or 2) take an existing mode such as MDA (as this is mono) and modify this to the new parameters?

I am assuming that 2) doesn't require to change the menu / program logic etc. I have only scanned the code but I noticed some decisions / selections are made based on (hi)resolution. If I insert a new (hi) resolution this might break this logic.

This all based on the assumption that adding a new profile / resolution would work in this way.

Thanks! Jan

[scrapcomputing]

Which graphics mode do you need to support at 640x400 ? Is it MDA, CGA or EGA? Each has its own challenges, so it is important to know which one you are trying to implement.

[jdelange]

The 640x400 graphics is a standard on its own. Perhaps MDA comes close, but I am not sure. It is supported by Borland Turbo Pascal and C++ for instance (below) and also by Lotus 123, and it is called ATT400. It is mentioned in the M24 Wiki, but I haven't come across a detailed description of it.

The pixel clock of the Olivetti is the standard 14.13... MHz. Together with the resolution I assume I have to work out the pixel rates and timings. I noticed these are hard coded in your code.

What makes the specific mode challenging?

[jdelange]

Trying to find a bit more info on the card. In this video it is described as a "super CGA" card. Starts at 9:44.

[scrapcomputing]

The challenge is the amount of RAM available. The frame buffer is currently set to 720x350. Increasing it to 720x400 (or even 640x400) won't work because the Pico 1 does not have enough RAM. So the only option is to use a Pico 2 which contains double the RAM.

[jdelange]

720 x 350 = 252k pixels < 256K, 640 x 400 = 256k pixels. Could this be a 2-step approach? First test the concept by taking 640 x 350 pixels from the feed (throw away 50 lines at the bottom or equally spaced over the frame) for now and see if we can get the timings etc to work and then the 2nd step could be to modify the buffer and display side. I realize that changing the buffer format messes up the hercules compatibility, so on the Pico 1 this would be a separate version. Perhaps on the Pico 2 with 720x400 we could support both.

[jdelange]

I am trying to build your code. I run into an error that I haven't been able to fix yet. Does this look familiar?

[build] C:/Users/jande/.pico-sdk/sdk/2.2.0/src/rp2_common/hardware_base/include/hardware/address_mapped.h:64:18: error: unknown type name 'uint64_t'
[build]    64 | typedef volatile uint64_t io_rw_64;
[build]       |                  ^~~~~~~~
[build] C:/Users/jande/.pico-sdk/sdk/2.2.0/src/rp2_common/hardware_base/include/hardware/address_mapped.h:13:1: note: 'uint64_t' is defined in header '<stdint.h>'; this is probably fixable by adding '#include <stdint.h>'
[build]    12 | #include "hardware/regs/addressmap.h"
[build]   +++ |+#include <stdint.h>

I tried the suggested fix to #include <stdint.h> at the top of the file, but then I get all kinds of other errors within that file.

[scrapcomputing]

This code that errors out is part of the SDK, it should compile fine with no changes.
Did you check with the pico-sdk documentation to see if your build environment is compatible ?

[jdelange]

Thanks. I have spent 2 days to get the code to compile in VS Code with the Pico environment on Windows with Copilot but I have failed to get it to work.

[scrapcomputing]

I don't have a windows system to try it on, sorry.

I would start with getting the pico-sdk examples compiled. If they work fine then it shouldn't be too hard to build this project because they are built in a similar way.

According to the pico-sdk README there should be instruction for windows in the manual:
"For detailed steps, instructions for other platforms, and just in general, we recommend you see Raspberry Pi Pico-Series C/C++ SDK"

[jdelange]

Thanks, appreciate that. Other projects compile fine. What does your environment look like?

[scrapcomputing]

I am using a Linux system. I just followed the instructions here: https://github.com/raspberrypi/pico-sdk?tab=readme-ov-file#unix-command-line to install the necessary tools.

After installing the tools (compilers, cmake, make) and downloading the pico-sdk, all you need to do is follow the instructions in the project's page: https://github.com/scrapcomputing/mceblaster#build-for-pico-rp2040-or-pico-2-rp2350

[jdelange]

Tanks! I have a laptop with Linux Mint. I will try my luck on that.

[scrapcomputing]

Oops I forgot to push all files to the repository, which is why you are getting the build error, sorry about that. I just fixed the repository (and the latest release), they should build fine now.

[jdelange]

Ah! Thanks. I removed my comment because I thought I was doing something wrong. Too many errors... Thanks for the update, that saves a lot of searching....

[scrapcomputing]

Let me know if you run into any other build issues. It should build fine with: cmake -DPICO_BOARD=pico -DCMAKE_BUILD_TYPE=Release -DPICO_FREQ=270000 -DPICO_SDK_PATH=<path to pico-sdk> ../src/ && make -j