Eric Herrmann asked 3 weeks ago
Hello, I purchased the LVGL + CYD course and to be honnest, even though I am just at the beginning of the course, I just find it is lacking a lot of explanations.
Here are my questions / Suggestions:
Why not explaining the content/structure of the eTFT and LVGL config files ? I really don’t like the ‘take this file copy/paste it in your project and you’re good to go’. What if I use a different board than the CYD, I would really like to understand the structure of those files in order to adapt them whenever I need.
Display buffer:
#define DRAW_BUF_SIZE (SCREEN_WIDTH * SCREEN_HEIGHT / 10 * (LV_COLOR_DEPTH / 8))
uint32_t draw_buf[DRAW_BUF_SIZE / 4];
Why those values? there’s no explanation
VSPI: there’s no explanation what it is, why we use it
Touch display:
x = map(p.x, 200, 3700, 1, SCREEN_WIDTH);
y = map(p.y, 240, 3800, 1, SCREEN_HEIGHT);
Why 3700 and 3800? There’s no explanation
So far I am very frustrated because it is more like copying / pasting without understanding what I am doing.
I really love your content but this one seems a bit too much vague….
Sara Santos Staff answered 3 weeks ago
Hi.
I’m sorry, and thank you for your feedback. I understand what you mean.
I believe Rui already answered your email with similar questions.
If you feel like the eBook is not what you’re looking for or you’re not satisfied with it, you can ask for a refund.
P.S.: I’m sorry for taking so long to get back to you. I’ve been sick for the past few days.
Regards,
Sara
Eric Herrmann answered 3 weeks ago
Hi Sara,
No worries, thanks for your answer, hope you’re getting better.
Indeed, I got an answer from Rui by email.
As I told him, I really appreciate your work and all the effort you putt on the web site and the courses.
I purchased almost all of your courses and this is the first time I feel a bit disappointed. I am still learning a lot, it is just that I feel it strange to have a book on LVGL not even talking about the content of the lvgl conf file which in my opinion is key. Of course the course is targetting the CYD but I guess we also purchase the course to use lvgl in a different context, with other boards.
This course feels to me that this is mainly copying/pasting and not really getting the details (see my initial questions). I would not know how to do with a different board.
Of course I cannot ask you to explain each single line but I believe my questions above are legitimate.
If you could just at least give me the explanation about this:
x = map(p.x, 200, 3700, 1, SCREEN_WIDTH);
y = map(p.y, 240, 3800, 1, SCREEN_HEIGHT);
Where are the 3700 and 3800 values coming from?
Thanks a lot!
Eric
Sara Santos Staff answered 3 weeks ago
Hi.
In that section, we are testing the touchscreen.
We’re basically converting raw touchscreen values (obtained experimentally) to the values corresponding to the actual touchscreen width and height. This is just a very rough estimation and a rough attempt of a basic calibration.
I believe you’re familiar with the Arduino Map function that we’re using.
The first parameter is the value read by the touchscreen, the next two values are the actual range of values read by the touchscreen, the last two, are the range that we want to convert to.
The 200 and 3700 in the first line are experimental values that we got after getting raw values from the touchscreen. The 200 and the 3700 are the minimum and maximum values that we got when we touched the edges of the x axis on the toucschreen.
The second line is the same, but referring to the y-axis.
I hope this makes sense. I hope it’s not confusing.
Regards,
Sara
Sara Santos Staff answered 3 weeks ago
Great.
I’ll mark this issue as resolved. If you need further help, you just need to open a new question in our forum.
Regards,
Sara