LCD Module Comparison (Teensy 4.0 SPI Connection)

Below is the list of SPI-connected LCD modules compared in this article.

Modules A, B, C, and E are mounted on base PCBs, while Module D is a bare panel with flex cable since a PCB-mounted version was not available.

In general, IPS panels offer wider viewing angles and less color shift compared to TN panels. In addition to resolution, the pixel pitch indicated by Dot Size is also a significant factor that greatly affects perceived image quality.

SPI is commonly called a 4-wire serial interface since it uses two data lines for Input/Output in addition to the serial clock and chip select. However, for LCD connections, data transfer is unidirectional (write-only from the device to the LCD module), so typically only one data line is used. In addition to these three wires (serial clock, chip select, and data), the DC and reset signals are used as auxiliary control lines. The signals are summarized as follows.

Basically, the CS, SCK, and MOSI signals directly related to SPI should be assigned to dedicated SPI I/O pins, while the DC and RST signals are controlled via GPIO.

Regarding power supply, some LCD modules have an onboard LDO regulator and support 5V input. However, even in that case, the I/O interface voltage remains 3.3V. In addition, many LCD modules have a backlight control pin.

First, here is the 128x160 pixel module using the ST7735 driver. A version with an SPI-connected microSD card slot was available.

Source: AliExpress, Amazon

There is also another version that appears to use the same LCD module but with a full-size SD card slot. The power supply supports 5V input, and when using 3.3V, you need to bridge J1 on the PCB. There is no signal line for backlight LED control.

The connection to Teensy 4.0 is as follows.

Since this is a TN panel, I checked the viewing angles. When oriented in portrait mode with the flex cable at the bottom, sweeping the horizontal (left-right) viewing angle while keeping vertical at 0 degrees (head-on) shows little change, with sufficient legibility even at about 45 degrees. When tilting only in the vertical direction while keeping horizontal at 0 degrees: viewing from the 6 o'clock direction, tilting just about 15 degrees noticeably increases overall brightness. Backlight bleed also becomes visible, but since the overall balance is maintained and the image quality appears at its best, this seems to be the intended optimal viewing angle. This remains consistent up to about 45 degrees. On the other hand, viewing from the 12 o'clock direction, tilting just about 15 degrees causes low-brightness areas to become extremely difficult to see. Meanwhile, the backlight bleeds through, severely distorting contrast and color balance, making anything other than high-brightness areas very hard to see.

This is an 80x160 pixel module using the ST7735 driver. Although the flex cable shape differs, it appears to be the same type used on the Sipeed Longan Nano board.

Source: AliExpress, Amazon

The connection to Teensy 4.0 is as follows.

Although this module has the lowest resolution among those introduced here, the fine dot size and wide viewing angles characteristic of IPS technology produce a very clean display. The backlight bleed is also well suppressed, giving blacks a beautiful appearance.

Among the LCD modules compared here, this one has the smallest dot size, delivering extremely high-definition image quality. The color reproduction and contrast are also excellent. The 16pt font appears quite small on this display, so when porting from an LCD with similar resolution, adjustments to layout and fonts may be necessary.

This LCD module also offers wide viewing angles characteristic of IPS panels. The display quality is on par with modules [B] and [C]. The dot size is neither too small nor too large, making it practical to use.

Since this is a TN panel, I checked the viewing angles. Compared to the other TN panel [A] ST7735 1.8" 128x160, the variation is noticeably less. Sweeping the horizontal (left-right) viewing angle shows little change. In the vertical direction, the best balance is achieved at about 15 to 20 degrees tilt toward the 6 o'clock direction. When viewed from the 12 o'clock direction, tilting 15 to 20 degrees does degrade contrast and color reproduction, but not to the point of severely impairing legibility, so this panel performs reasonably well for a TN type.

I also recorded a video. Due to camera exposure, high-brightness areas may appear to have lower saturation than they actually do; in reality, the colors look a bit better.

I used a customized version of the graphicstest project included with Adafruit's LCD library for testing. It was built and used on a Teensy 4.0 board with the Visual Studio Code + PlatformIO extension environment.

For the project for modules [A] through [D] using ST7735 and ST7789 driver ICs, please refer to the following.

For the project for module [E] using the ILI9341 driver IC, please refer to the following.