Enable setting of GUI resolution, enable user input of precise values for GUI settings, add hardware support for USB and GPIO touchscreen

[michelemaroni]

Hello,

Thanks again for the experimental build.
I made some tests and I've come up with some new potential improvements.

1. Enable the user to set the resolution for the GUI:
   Editing some configuration file before powering on would be sufficient.

2. Enable user input of precise values for GUI settings:
   Basically sometimes the steps changes provided by arrows are too big. If a user could directly enter the desired value (tapping twice on the value or somethin like that) it would be very useful. For the moment this is possible by manually editing the patches correct?

I'd also change the unit and the values for some sections, but I need more time to carefully check, note them down and report to you. E.g. the tuning of oscillators would be better set using the cents as a unit, and probably adding also a key transpose feature for each available oscillator. This could be achieved by multiplying the oscillator base frequency for a contants.

For key transposition, one oscillator (O1) is set to a frequency and the second one (O2) is set to a frequency that corresponds to a specific interval in semitones:
O2 = Nr_Semitones*12√2*O1

For tuning by cents it would be:
O2=Nr_Cents*1200√2 *O1

Then for two active oscillator I would have:
O2 = ΔFreq_of_Cents + ΔFreq_of_Semitones +O1

Let me know if this is confusing, I'd try to explain it better.

3. Add support for resistive and capacitative touchsreen via gpio or usb:
   I understand that hardware support for any user device would be way beyond you interest and resources, however the majority of users buy chinese display are all based on the waveshare chipsets. The most common are display of 3.5-5 (generally resistive touch via GPIO) and 7 inches (generally capacitative touch via usb) displays. How difficult and time consuming would be to add support for those?

[rsta2]

Thanks for the new suggestions for improvements.

With the GUI you hit a difficult point. It is kept simple by intention, all parameters use the same up/down buttons and the positions of the different controls are fixed and do work with the 800x480 screen resolution only, which work with most displays and the official 7" Raspberry Pi touchscreen, which is already supported by the Circle framework and by MiniSynth Pi. To support the 3.5" Waveshare display would require a totally different arrangement of the controls and more tabs, because the display resolution is much smaller.

For the moment I would focus on the supporting the 5" or the 7" Waveshare display. I would buy one of these displays to be able to test it, but not both. So it would be good to know, which display is used by more synth users? The support has to added to Circle first. I would stay with the 800x480 resolution at first. Is there a datasheet for the GPIO or USB touchscreen function somewhere?

Editing the parameters directly could be probably implemented, by using an additional popup window. The user taps on the parameter value and the popup opens, where the new value can be entered. I will have to open a screen keyboard for this purpose.

The modifications for the oscillator section should be possible to make. I will need another two fields for the cents detune and the key transpose in the GUI.

[michelemaroni]

Hi,

I couldn't find a datasheet for the display, however there is an official repo with the drivers for the different displays and a wiki.
I'd guess that the majority of the user go for the 5'in display, but it comes in two different flavours: the one with resistive touch uses and the one with capacitative touch.

Then I'd drop the plan for the 3.5 display then, since not only is difficult, but also those displays are very limited: I had one and gave it away, and upgraded to a 7 inch.
Would scaling up the gui resolution to 1024×600 be feasible?

[rsta2]

Thanks for the info about the different displays and the links. I would suggest the following: I will buy a 5 inch HDMI display (probably LCD (B)) with USB touch function. You have the 7 inch LCD (C). So we can test MiniSynth Pi with both display sizes and I have to implement the USB touch interface only, at least for now. It should be possible to provide two (fixed) screen sizes (800x480 and 1024x600) in a way, that on the larger display the different controls get more room.

I guess, I have to place the different parameters on the MAIN tab in a different way in the GUI at first, because there is not enough room for new parameters for the oscillator any more. Maybe there must be another new tab (e.g. one "VCO / VCF" tab, instead of MAIN, and one "VCA / FX" tab)? On the other hand, I think, it's good to have everything "in sight", without the need to change the tabs all the time.

What do you think?

[michelemaroni]

The idea of splitting the GUI by section sounds actually good, it is for example the same strategy used in high end synth and workstations like the kronos. The important thing is having a meaningful grouping of parameter within the same window.

I'd propose to put VCO and LFO in one tab, the EG in another and then one for the FXs where we could foresee slots for different fx to be chained together.

About the display, yes i have the one with usb , and sounds like a good strategy.

[rsta2]

So I think, we should go this (display) way. I've ordered a 5 inch Waveshare LCD B with HDMI and USB.

I think, for a start I will add one new tab to the GUI to get more room for the VCO. The parameters have to be re-ordered any way later.

Please note, that this is not a high performance audio design. With 24 parallel voices I have already about 60% of the possible CPU time used to calculate the audio samples on RPi 2-4. It's already more on the RPi 1 with 4 voices. There is one point for improvement on the RPi 2-4: It's currently running at 600 MHz only, while for instance the RPi 3B supports 1200 MHz. But you need a fan to continuously use this and not anybody has one.

[michelemaroni]

I see.
Then, I would not add more voices since 24 is actually a lot.

The way "classic" analog synths worked is that you had a certain number of voices available (5-6-8), and then you built the sounds according to the number of voices, by reducing polyphone for complex sounds with layered voices or by increasing polyphony through reduction of layered voices.

So basically if I, as a user, develop a sound with many voice then I would reasonably expect a reduction in polyphony.

An option to further increases the number of voices if necessary could be to add a parameter in a configuration file that unlocks additional voices, but with a disclaimer/warning the user is warned to do so only if he can cool his device.

[rsta2]

Thanks for explaining this! I think, the number of polyphonic voices can be made configurable, as suggested. I got the 5" Waveshare touchscreen. Generally it is working, but not with touch yet, of course. I'm currently preparing a new Circle release and will come back next week.

[rsta2]

Attached there is a first test version of MiniSynth Pi, which works with the Waveshare 5 inch LCD (B) touch screen and should work with the 7 inch LCD (C) too. I'm not totally sure, if it works with the 7 inch version and want to test this here. If it does not work, we have to step back and test with an other program.

Please don't wonder about the unusual GUI. I only modified the program, that it auto-detects the screen size, but effectively it still only uses 800x480 pixels. This test is specially for the touch function, not for the GUI itself. You only have to replace the file kernel7.img in the archive, I did send you earlier. The 5 inch version needs some calibration info, but I guess, the 7 inch version works without it.

kernel7.zip

[michelemaroni]

Unfortunately it does not work.

[rsta2]

OK, that was possible, unfortunately I was too quick. Thanks for testing. Then we have to go a step back and need some information from your touchscreen (vendor and device ID, HID descriptor). Attached there is another kernel image, which writes a file circle.log on the SD card. Can you please run it, with the touchscreen connected. You only need to replace the file kernel7.img with the one from the extracted .zip archive. Please run it once and copy the file circle.log from the SD card and post it here. The touchscreen will not work yet. Thank you!

kernel7.zip

[michelemaroni]

Hello, sorry for the late reply, had quite a busy week.

Thanks for the image, I run the test and got you the log file that you asked for.

Please find it attached below.
circle.log

Please let me know if there is anything else that I can help you with in the meantime.

Best regards

[rsta2]

No problem and thanks for testing! I was able to retrieve the needed information from the log file.

The previous test did not work, because your touchscreen has a different USB vendor and device IDs from my own touchscreen. After some reading on the Internet, I expected them to use the same USB chip and vendor/device IDs, but they don't. Also the format of the HID touchscreen reports is different.

I think, I should try to find a generic solution for all USB HID compatible touchscreens here, instead of a specific driver for our two screens, but this requires additional work. I hope, I can complete this until next weekend and will post a new test image then.

[rsta2]

I have implemented a generic USB touchscreen driver. It works on my Waveshare 5 inch LCD (B) and hopefully on all USB touchscreens, but I expect quirks with some touchscreens, so there is some uncertainty. It would be great, if you could test this driver with the attached test kernel image on your own touchscreen.

The test program initializes the touchscreen and waits for touch events. When a finger is pressed on the display, a Finger #N down at X / Y message should be displayed on the screen, where N is the finger ID (1..10) and X / Y is the pixel position of the finger. Other messages are Finger #N moved to X / Y and Finger #N up. According to the HID report descriptor, your screen may support up to six fingers pressed at once.

If it generally works, please have a look at the X / Y coordinates. The first value should range between 0 and 1023 for your screen and the second between 0 and 599. If this is not the case, your screen needs some calibration for this driver. I would tell you next, how this works.

kernel7.zip

[michelemaroni]

Hi sorry for the delayed answer.

I made the test with the image you sent me and the driver worked very nicely: touche seemed accurate and very responsive.

The values were a bit different for my screen but i guess is due to the pixel size.

Thank you.

Best,

MM