{"id":14922,"date":"2023-06-26T10:32:16","date_gmt":"2023-06-26T05:02:16","guid":{"rendered":"https:\/\/fastbitlab.com\/?p=14922"},"modified":"2023-08-17T16:42:11","modified_gmt":"2023-08-17T11:12:11","slug":"ltdc-layer-initialization-and-windowing-step-by-step-guide","status":"publish","type":"post","link":"https:\/\/fastbitlab.com\/blog\/ltdc-layer-initialization-and-windowing-step-by-step-guide\/","title":{"rendered":"STM32-LTDC, LCD-TFT, LVGL(MCU3) Lecture 39| LTDC Layers initialization coding and windowing explanation"},"content":{"rendered":"
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LTDC Layers initialization coding and windowing explanation<\/strong><\/span><\/h1>\n
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In the previous article, we explored a few registers of the LTDC layers. In this article, let’s continue with our coding and create another function called “LTDC Layer Init”. This function will be responsible for initializing the LTDC layer according to our application requirements.<\/span><\/p>\n

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To initialize the LTDC layer, you need to follow these steps:<\/span><\/p>\n

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  1. Configure the pixel format of the layer’s framebuffer.<\/span><\/li>\n
  2. Configure the constant alpha and blending factors, namely BF1 and BF2.<\/span><\/li>\n
  3. Configure the layer position (Windowing).<\/span><\/li>\n
  4. Configure the frame buffer address.<\/span><\/li>\n
  5. Optionally, configure the default color of the layer (usually black color is used by default).<\/span><\/li>\n
  6. Configure the pitch, line length, and line numbers of the frame buffer.<\/span><\/li>\n
  7. Activate immediate reload. This means storing the values from the shadow registers to the real registers. All the configurations mentioned above are stored in the shadow registers, so activating immediate reload is necessary.<\/span><\/li>\n
  8. Enable the layer.<\/span><\/li>\n<\/ol>\n

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    \"Figure
    Figure 1. LTDC layers initialization steps<\/span><\/figcaption><\/figure>\n

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    You can easily code these steps by referring to the reference manual.<\/span><\/p>\n

    Now, I will explain how to configure the position of the layer and how the windowing works.<\/span><\/p>\n

    Let’s discuss the configuration items for the horizontal position of the layer window.<\/span><\/p>\n

    \"LTDC
    Figure 2. Layer window horizontal position configuration items<\/span><\/figcaption><\/figure>\n

    There are 2 configuration items. WHSTOPS(Start) and WHSPPOS(Stop).<\/span><\/p>\n

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    \"LTDC
    Figure 3. LTDC Layerx Window Horizontal Position Configuration Register<\/span><\/figcaption><\/figure>\n

    In the LTDC Layerx Window Horizontal Position Configuration Register, you can see the start position and the stop position(Figure 3).<\/span><\/p>\n

    How to calculate the start position and stop position? You can follow the method below. <\/span><\/p>\n

    WHSTOPS(Start) = AHBP+H_start+1<\/b><\/span><\/p>\n

    WHSPPOS(Stop) = AHBP+H_start+Layer_width+1(<=AAW)<\/b><\/span><\/p>\n

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    1. WHSTOPS (Start):<\/span><\/strong><\/span>\n