MIPI Display Bus Interface (DBI)

The MIPI DBI driver class implements support for MIPI DBI compliant display controllers.

MIPI DBI defines 3 interface types: * Type A: Motorola 6800 parallel bus

  • Type B: Intel 8080 parallel bus

  • Type C: SPI Type serial bit bus with 3 options:

    1. 9 write clocks per byte, final bit is command/data selection bit

    2. Same as above, but 16 write clocks per byte

    3. 8 write clocks per byte. Command/data selected via GPIO pin

Currently, the API only supports Type C controllers, options 1 and 3.

API Reference

group mipi_dbi_interface

MIPI-DBI driver APIs.

Defines

MIPI_DBI_MODE_SPI_3WIRE

SPI 3 wire (Type C1).

Uses 9 write clocks to send a byte of data. The bit sent on the 9th clock indicates whether the byte is a command or data byte 

      .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-
SCK  -' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-'

     -.---.---.---.---.---.---.---.---.---.---.---.---.---.---.---.-
DOUT  |D/C| D7| D6| D5| D4| D3| D2| D1| D0|D/C| D7| D6| D5| D4|...|
     -'---'---'---'---'---'---'---'---'---'---'---'---'---'---'---'-
      | Word 1                            | Word n

     -.                                                              .-
CS    '-----------------------------------------------------------'

MIPI_DBI_MODE_SPI_4WIRE

SPI 4 wire (Type C3).

Uses 8 write clocks to send a byte of data. an additional C/D pin will be use to indicate whether the byte is a command or data byte 

      .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-.
SCK  -' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '---

     -.---.---.---.---.---.---.---.---.---.---.---.---.---.---.---.---.-
DOUT  | D7| D6| D5| D4| D3| D2| D1| D0| D7| D6| D5| D4| D3| D2| D1| D0|
     -'---'---'---'---'---'---'---'---'---'---'---'---'---'---'---'---'-
      | Word 1                        | Word n

     -.                                                                  .-
CS    '---------------------------------------------------------------'

     -.-------------------------------.-------------------------------.-
CD    |             D/C               |             D/C               |
     -'-------------------------------'-------------------------------'-

MIPI_DBI_MODE_SPI_4WIRE_16BIT

SPI 4 wire (Type C4).

Uses 16 write clocks to send a byte of data. Generic data (GRAM) is passed through in 16 bit alignment with odd-length stuffing. an additional C/D pin will be use to indicate whether the byte is a command or data byte 

      .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-. .-.
SCK  -' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '-' '---

     -.---.---.---.---.---.---.---.---.---.---.---.---.---.---.---.---.-
DOUT  |D15|D14|D13|D12|D11|D10| D9| D8| D7| D6| D5| D4| D3| D2| D1| D0|
     -'---'---'---'---'---'---'---'---'---'---'---'---'---'---'---'---'-
      | Word 1             (stuffing) :                        (byte) |

     -.                                                                  .-
CS    '---------------------------------------------------------------'

     -.---------------------------------------------------------------.-
CD    |                              D/C                              |
     -'---------------------------------------------------------------'-

MIPI_DBI_SPI_CONFIG_DT(node_id, operation_, delay_)

initialize a MIPI DBI SPI configuration struct from devicetree

This helper allows drivers to initialize a MIPI DBI SPI configuration structure using devicetree.

Parameters:

  • node_id – Devicetree node identifier for the MIPI DBI device whose struct spi_config to create an initializer for

  • operation_ – the desired operation field in the struct spi_config

  • delay_ – the desired delay field in the struct spi_config’s spi_cs_control, if there is one

Functions

static inline int mipi_dbi_command_write(const struct device *dev, const struct mipi_dbi_config *config, uint8_t cmd, const uint8_t *data, size_t len)

Write a command to the display controller.

Writes a command, along with an optional data buffer to the display. If data buffer and buffer length are NULL and 0 respectively, then only a command will be sent.

Parameters:

  • dev – mipi dbi controller

  • config – MIPI DBI configuration

  • cmd – command to write to display controller

  • data – optional data buffer to write after command

  • len – size of data buffer in bytes. Set to 0 to skip sending data.

Return values:

  • 0 – command write succeeded

  • -EIO – I/O error

  • -ETIMEDOUT – transfer timed out

  • -EBUSY – controller is busy

  • -ENOSYS – not implemented

static inline int mipi_dbi_command_read(const struct device *dev, const struct mipi_dbi_config *config, uint8_t *cmds, size_t num_cmd, uint8_t *response, size_t len)

Read a command response from the display controller.

Reads a command response from the display controller.

Parameters:

  • dev – mipi dbi controller

  • config – MIPI DBI configuration

  • cmds – array of one byte commands to send to display controller

  • num_cmd – number of commands to write to display controller

  • response – response buffer, filled with display controller response

  • len – size of response buffer in bytes.

Return values:

  • 0 – command read succeeded

  • -EIO – I/O error

  • -ETIMEDOUT – transfer timed out

  • -EBUSY – controller is busy

  • -ENOSYS – not implemented

static inline int mipi_dbi_write_display(const struct device *dev, const struct mipi_dbi_config *config, const uint8_t *framebuf, struct display_buffer_descriptor *desc, enum display_pixel_format pixfmt)

Write a display buffer to the display controller.

Writes a display buffer to the controller. If the controller requires a “Write memory” command before writing display data, this should be sent with mipi_dbi_command_write

Parameters:

  • dev – mipi dbi controller

  • config – MIPI DBI configuration

  • framebuf – framebuffer to write to display

  • desc – descriptor of framebuffer to write. Note that the pitch must be equal to width. “buf_size” field determines how many bytes will be written.

  • pixfmt – pixel format of framebuffer data

Return values:

  • 0 – buffer write succeeded.

  • -EIO – I/O error

  • -ETIMEDOUT – transfer timed out

  • -EBUSY – controller is busy

  • -ENOSYS – not implemented

static inline int mipi_dbi_reset(const struct device *dev, uint32_t delay)

Resets attached display controller.

Resets the attached display controller.

Parameters:

  • dev – mipi dbi controller

  • delay – duration to set reset signal for, in milliseconds

Return values:

  • 0 – reset succeeded

  • -EIO – I/O error

  • -ENOSYS – not implemented

  • -ENOTSUP – not supported

struct mipi_dbi_config
#include <mipi_dbi.h>

MIPI DBI controller configuration.

Configuration for MIPI DBI controller write

Public Members

uint8_t mode

MIPI DBI mode (SPI 3 wire or 4 wire)

struct spi_config config

SPI configuration.

struct mipi_dbi_driver_api
#include <mipi_dbi.h>

MIPI-DBI host driver API.