Questions about tftlcd hardware interfaces and drivers

When designing the tftlcd hardware driver circuit, we will find that the interfaces of the tftlcd bare screen (the first purchased component) are not similar, so the driver circuit design needs to be different.

The essence of tftlcd liquid crystal is dot matrix.

Task of tftlcd driver circuit

To display images, you must constantly scan them. The so-called driving circuit completes the work of constantly scanning the LCD, usually with a frame rate of 30 ~ 60Hz to make people unable to see the screen jitter.

The MCU sends the display content to the driving circuit, and then the driving circuit continuously scans the data to the display for display. It can be seen that the driver circuit must have a buffer to cache the display content. Of course, the larger the buffer, the larger the corresponding screen storage or the more virtual pages that are supported.

In a word, the task of the driving circuit is to receive the MCU display data and scan the display at enough Frame Rate on the screen.

Differences between bare screens purchased on the market

The 3.2 inch or so small screen purchased on the market usually carries a driver chip, such as ili9341. The driver chip contains a buffer zone and scan display circuit. For users, no additional driver circuit is required. Interfaces provided by these screens include SPI/RGB/8080cpu. Different interfaces can be controlled by MCU of different grades. SPI can be driven by 51 single-chip microcomputer, while CPU interfaces can be driven by stm32. RGB interfaces can be driven by S3C2440 with LCD driving circuit.

The 4.3-inch bare screen purchased on the market usually does not provide the driver chip, which means that the driver circuit needs to be designed by the user. Commonly Used driver chips include ra8875. The interface provided by the large screen is different from that provided by the small screen. The 4.3-inch screen on the tq2440 Development Board is an RGB interface.

Comparison between ili9341 and LCD interfaces and S3C2440 and LCD Interfaces

The 3.2-inch LCD driven by ili9341 is visible. The interface between the LCD and the driver chip is s720 ~ S1 and g320 ~ G1 is to use these control lines to scan the LCD. 4.3-inch LCD directly driven by S3C2440, which uses the RGB interface to scan the LCD (similar to the camera interface, split-frame synchronous signal, line synchronous signal, pixel clock, data line ).

Update cache frequency and scan display frequency

When we watch a video, the video frame needs to be written to the video memory at a certain frequency (which can be considered as the buffer zone of the driver chip, the buffer content is displayed on the screen with a scanning frequency, which is different. The frequency of screen scanning is between 30 and 30 ~ In the range of 60Hz, the screen flushing frequency should be low because the screen flushing frequency is too high.

S3C2440 is connected to LCD screen with ili9341

Ili9341 is connected to stm32 with an 8080cpu interface, while the LCD controller connected to S3C2440 should use an RGB interface. This is actually a bit odd in the middle. The LCD controller of S3C2440 will constantly refresh its memory to the memory of ili9341, and ili9341 will refresh its memory to the LCD. Of course, this ili9341 is actually a bit redundant.

 

Questions about tftlcd hardware interfaces and drivers