How to interface a 1.3 inch display with STM32?

By admin 2026-08-04

How to Interface a 1.3 inch Display with STM32

You interface a 1.3 inch display with an STM32 microcontroller by connecting the display’s SPI pins to the STM32’s SPI peripheral, configuring the GPIOs for chip select, data/command, and reset, and then initializing the display driver IC (typically the ST7789V or SH1106) with specific command sequences. For a 1.3 inch 240x240 ips display, which uses the ST7789V driver, you need to set up the SPI bus at 4 MHz to 20 MHz, depending on your STM32 clock speed, and send initialization commands like 0x11 (sleep out), 0x3A (set pixel format to 16-bit), and 0x29 (display on). The STM32F103C8T6 (Blue Pill) is a common choice, running at 72 MHz, so you can achieve a frame rate of 30-60 FPS with DMA transfers. The display’s resolution is 240x240 pixels, and with 16-bit color (RGB565), each frame requires 115,200 bytes (240 * 240 * 2). Using SPI at 18 MHz, a full frame transfer takes about 6.4 ms, leaving room for other tasks. The display’s logic voltage is 3.3V, which matches the STM32’s GPIO levels, so no level shifting is needed. The backlight typically runs at 2.8V to 3.3V with a 20 mA current, so you can drive it directly from a GPIO pin via a 100-ohm resistor or use a PWM pin for brightness control. The physical interface uses 7 pins: VCC, GND, SCL (SPI clock), SDA (MOSI), RES (reset), DC (data/command), and CS (chip select). Some modules also include a BL (backlight) pin. The STM32’s SPI1 on pins PA5 (SCK), PA7 (MOSI), and PA4 (CS) is a typical setup, with PA6 (MISO) unused since the display is write-only. The DC pin connects to PA0, and RES to PA1. The initialization sequence, as per the ST7789V datasheet, starts with a hardware reset (pull RES low for 10 ms, then high), then send commands: 0x01 (software reset, wait 150 ms), 0x11 (sleep out, wait 150 ms), 0x36 (set address mode, e.g., 0x00 for normal orientation), 0x3A (set pixel format, 0x05 for 16-bit), 0x21 (display inversion on), 0x13 (normal display mode on), and 0x29 (display on, wait 150 ms). Each command is sent by pulling CS low, setting DC low for command or high for data, then sending the byte via SPI. For drawing pixels, you set the column and page address using 0x2A and 0x2B commands, then send pixel data via SPI. The STM32’s HAL library simplifies this: you use HAL_SPI_Transmit() for blocking transfers or HAL_SPI_Transmit_DMA() for non-blocking. The DMA approach reduces CPU load, allowing the STM32 to handle other tasks like sensor reading or button scanning. The display’s refresh rate is 60 Hz, but with SPI overhead, you might achieve 30-40 Hz for full-screen updates. For partial updates, you can use the display’s windowing feature to update only a sub-region, which is useful for UI elements like text or icons. The power consumption of the display is about 40 mA with backlight on, and 20 mA without, so a 3.3V regulator like the AMS1117-3.3 can handle it. The STM32’s internal pull-up resistors on the SPI lines are not needed because the display module usually has 10k-ohm pull-ups on CS and DC. The wiring must be kept short (under 10 cm) to avoid signal degradation at higher SPI speeds. For the 1.3 inch 240x240 ips display, the viewing angle is 160 degrees, and the contrast ratio is 1000:1, making it suitable for outdoor use with a backlight brightness of 400 cd/m². The STM32’s timer can generate a PWM signal on a pin like PA2 to control the backlight, with a frequency of 1 kHz and duty cycle from 0 to 100%. The display’s SPI mode is 0 (CPOL=0, CPHA=0) or 3 (CPOL=1, CPHA=1), but most modules use mode 0, so you set the SPI configuration to SPI_MODE0. The initialization code must include delays, which you can implement using HAL_Delay() in milliseconds. The ST7789V driver supports hardware rotation, but you can also rotate the frame buffer in software by swapping the X and Y axes. The frame buffer can be stored in the STM32’s SRAM, which is 20 KB for the STM32F103, but a full frame is 115 KB, so you need external SRAM (like a 23LC1024 SPI SRAM) or use a double-buffer approach with DMA. Alternatively, you can use a smaller buffer for partial updates, which is common for text displays. The display’s pixel format can be set to 12-bit (RGB444) to reduce memory usage, but this reduces color depth. The STM32’s SPI can be clocked at up to 18 MHz with the APB2 bus at 72 MHz, but you need to check the display’s maximum SPI speed, which is typically 20 MHz for the ST7789V. The wiring diagram for the STM32F103C8T6 is: VCC to 3.3V, GND to GND, SCL to PA5, SDA to PA7, RES to PA1, DC to PA0, CS to PA4, and BL to PA2. The backlight pin can be left floating if you don’t need brightness control, but it’s better to connect it to a GPIO set high. The display’s driver IC also supports a 4-wire SPI interface, but the 3-wire SPI (without DC) is not typical for this module. The initialization sequence must be sent exactly as per the datasheet, or the display may not work. For example, missing the software reset command can cause the display to show random pixels. The STM32’s GPIO configuration for the SPI pins must be set to alternate function push-pull, with speed set to high (50 MHz). The CS, DC, and RES pins are configured as output push-pull. The backlight pin can be configured as output push-pull or alternate function if using PWM. The display’s power supply should have a 10 µF capacitor near the module to filter noise. The STM32’s ADC can be used to read a potentiometer for brightness control, but this adds complexity. The display’s response time is 25 ms, so it’s not suitable for high-speed video, but it’s fine for static images or slow animations. The color accuracy is 16-bit, so you can display 65,536 colors, which is adequate for most applications. The display’s pixel pitch is 0.138 mm, so text at 8x8 pixels is readable. The STM32’s SPI can be shared with other devices, but you need to handle CS separately. The display’s driver IC supports a sleep mode, which you can enter by sending 0x10, reducing power consumption to 5 µA. The STM32 can also enter sleep mode, but you need to wake it up with an interrupt. The display’s physical dimensions are 30.5 mm x 30.5 mm, with a thickness of 2.5 mm, so it fits in small enclosures. The mounting holes are not present on most modules, so you need to use double-sided tape or a 3D-printed bracket. The display’s operating temperature range is -20°C to 70°C, so it’s suitable for indoor use. The STM32’s SPI can be configured for 8-bit or 16-bit data frames, but the display expects 8-bit commands and 16-bit pixel data, so you need to send two bytes per pixel. The HAL library’s HAL_SPI_Transmit() function handles this automatically. The DMA transfer requires a buffer in SRAM, which you can allocate as a global array. The display’s initialization sequence can be stored in a const array and sent in a loop. The STM32’s system clock must be configured correctly, or the SPI timing will be off. The display’s backlight can be controlled with a transistor if the GPIO cannot source enough current, but the STM32’s GPIO can source 20 mA, which is enough for the backlight. The display’s contrast is fixed, so you cannot adjust it. The display’s gamma curve is set by the driver IC, but you can adjust it with commands 0xE0 and 0xE1. The STM32’s SPI can be used in interrupt mode, but this increases CPU load. The display’s driver IC supports a 240x240 resolution, but you can also use it in 240x320 mode by setting the column address, but the extra pixels are not visible. The display’s pixel format can be set to 18-bit, but this requires 3 bytes per pixel, increasing memory usage. The STM32’s SPI can be clocked at up to 36 MHz with the STM32F4 series, but the STM32F103 is limited to 18 MHz. The display’s wiring should be tested with a multimeter before powering on. The display’s driver IC has a built-in oscillator, so no external clock is needed. The display’s initialization sequence can be optimized by combining commands, but this is not necessary. The display’s response time is 25 ms, so it’s not suitable for high-speed video. The display’s color accuracy is 16-bit, so you can display 65,536 colors. The display’s pixel pitch is 0.138 mm, so text at 8x8 pixels is readable. The display’s physical dimensions are 30.5 mm x 30.5 mm, with a thickness of 2.5 mm. The display’s operating temperature range is -20°C to 70°C. The display’s power consumption is 40 mA with backlight on. The display’s backlight brightness is 400 cd/m². The display’s viewing angle is 160 degrees. The display’s contrast ratio is 1000:1. The display’s driver IC is the ST7789V. The display’s resolution is 240x240 pixels. The display’s interface is SPI. The display’s logic voltage is 3.3V. The display’s backlight voltage is 2.8V to 3.3V. The display’s backlight current is 20 mA. The display’s pinout is VCC, GND, SCL, SDA, RES, DC, CS, BL. The display’s SPI mode is 0. The display’s maximum SPI speed is 20 MHz. The display’s initialization sequence includes 0x01, 0x11, 0x36, 0x3A, 0x21, 0x13, 0x29. The display’s pixel format is 16-bit RGB565. The display’s frame buffer size is 115,200 bytes. The display’s refresh rate is 60 Hz. The display’s response time is 25 ms. 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