Triple M33 low-power portable display

It is powerful and low-power, capable of driving at least 10.1 "800x1280 MIPI screens, and MIPI CSI and NPU have also been integrated. Preparing to start designing NGFF modules compatible with BK7258 for rapid validation.

We tested three types of transflective LCD screens to determine which one consumed less current. Their dimensions, resolutions, and zero-backlight current are as follows:

3.0" 240x400 RLCD   5mA
4.0" 272x480 RLCD   10mA
5.0" 800x480 RLCD   56mA

We have found a large-sized round smartwatch display with a resolution of 1.75" 466x466 AMOLED. On its left side is a maximum square display with a resolution of 2.16" 480x480 AMOLED. It boasts excellent display quality and low operating current. The current consumption is 75mA@5V when GPS is enabled. When GPS is turned off, the current consumption drops to 40mA.  Therefore, the total current consumption is CPU + 2x AMOLED = 40mA@5V.

These two round screens are only different in size, and their resolution is exactly the same.

Simulated aviation instruments and motorcycle instruments use such screens.

Square LCD screens are very common in instruments, especially the 4" 480x480 is widely used in 86 boxes.

The resolution of the whole device is 480x960, which is divided into two 480x480 screens. The first control screen is on the left, and the GPS map display screen is on the right. The display and black screen of the second screen can be controlled separately.

Since the simulator uses the code of lvgl 9, and the SDK of BK7258 is based on lvgl 8.x, it needs to be properly modified to port.

PCB uses 4 layers of 1mm thickness and 0.3/0.45mm drilling. 

 There are two LCD sockets on the PCB, one is 40P SPI+RGB666+TP. There are many types of this small screen with capacitance touch. Generally, the SPI port needs to be used to initialize the LCD screen chip. 
 The other is an ordinary 40P 4.3" 5" 7" regular TFT screen, which uses a separate 6P TP FPC to connect a capacitive touch screen. 
 Typical screen sizes and resolutions are listed behind the PCB.

6x2.2uF 0201 capacitors and GC2145 BGA chips are very small and need the help of a magnifying glass. 
 The lens holder of 6x6MM is indeed very small, which is limited by the resolution and size of 1/5" sensor, and the area that contains 6 capacitors, which is the best configuration.

We used BK7258 to design another PCB that supports RGB+SPI+TP and RGB interface displays, which can support displays of a wide range of sizes and resolutions. This PCB removes the 4G module. We marked the list of supported displays on the back of the PCB.

We chose a 5" 800x480 reflective display as an application with a separate Goodix capacitive touch screen. There is no need to turn on the backlight in the sun, which can save a lot of energy and extend the battery life.

We tested this display on the T113 EVK as shown in the following figure: