TFTLCD Library¶

NOTE (2013-03-25) Tested with both mbed LPC1768 and Freedom KL25Z. -todor

A TFT LCD driver library, which at the moment provides support for the following display controllers: HX8340-B (serial interface), SSD1289 (16-bit interface), ST7735-R (serial interface), ILI9325/ILI9328 (16-bit interface).

As I am acquiring and testing out new displays, I decided to combine all ported drivers into one library as with the original work done by Henning. However I also had as a goal to make the code maintenance and readability easier/better, so the code has been heavily refactored to make full use of C++ facilities as inheritance and access control. I extracted the common pieces of code into a base class, which every driver inherits and only the controller-specific side is provided in the actual driver - things like initialization, addressing, data transfer, etc.

Another nice extension is that the display's backlight can now be controlled through the driver. Either a simple on/off method of control could be selected, or the brightness can be set through use of PWM (the latter placing some restrictions on which pins can be used for this, as mbed offers hardware PWM on only 6 pins).

I also plan to add support for touch screens as part of the library. The goal is to grow this piece of software into a lightweight graphics widgets library, which can be used to construct control screens with buttons or menus in a speedy and intuitive way.

Changes¶

2013-07-21¶

• Fixed the sleep/wake-up functions of the ILI9328 driver.

2013-06-15¶

• Added driver for ILI9328 (works with ILI9325) controller, 16-bit data bus. Screen rotation works as usual with the TFTLCD library, but for now only RGB565 color depth is working and you can use both 65K and 262K color space with this driver. But for some reason the sleep function is not behaving as expected; I am working on this.
• This is only on my to-do list for now - haven't really had the time yet - but I am going to refactor the library a bit to allow use of GPIO ports for data transfers instead of DigitalOut: faster and cleaner that way. For those who are using it already in a working design and cannot repurpose the pins anymore, the current way it's working will still be available; I am hoping not to tear up the public interfaces of the library (... too much). Anyway, since I am at it, I will also try to add support for multiple bus interfaces to drivers that support it (i.e. both 8bit and 16bit use of ILI932x or SSD1289). Thought this might be a good place to give you guys the heads-up.

2013-01-25¶

• Replaced all existing fonts from the UTFT library with the free Terminus font. Two different sizes are provided: 8x12 pixels and 16x28 pixels. I found the old fonts not so good looking and then they supported only the ASCII codes in the range 30 (space) to 126 (the tilde ). The 7segment font didn't even implement anything else than the numbers from 0 to 9 - so it was unusable for anything (one couldn't even display the time or date as it lacked the colon [:] or the period [.] or the slash [/] or the space [ ] characters). So I completely revamped the fonts and added Terminus as the new default with its 2 sizes. Further more I added in both sizes most of the characters up to ASCII code 255. For any code not in there, the space character is substituted. In the case, when you already have provided your own fonts, please have a look at the API changes in the files <terminus.h> and <terminus.cpp>: I promise you whatever time you spent designing your own font, it is not wasted; you merely need to add a second array, which describes which ASCII codes are available in your font, and their byte offset in the original character bitmap array; and a struct to tie all parts together and describe the character size. I am sorry for breaking the old API, but you will like the change and new options it brings you. Now you can insert any char above 127 up to code 255 (if available, of course) with its hex representation, e.g displaying the current temperature would look something like 85\xB0 F or 26\xB0 C (the space in between degree and F or C is needed because both F and C are used in hex numbers, so \xB0F is interpreted as ASCII code 2831 instead of ASCII code 176, followed by the temperature scale denomination; if you insist on avoiding the space, you could write 85\xB0\x46 which will be displayed correctly as 85°F). You can either look up the ASCII code you need on Google or Bing, or just look at what's available - how it looks and its hex value - in the comments in <terminus.cpp>.
• Added PWM backlight control. If you intend to use this, please make sure that control pin is either one of p21, p22, p23, p24, p25, or p26, as only they support hardware PWM. Please be aware that the mbed pins do not have much juice behind them, so if your display's backlight requires a lot of current, you are better off interfacing through as small signal transistor or a MOSFET. For the rest please consult the updated Doxygen documentation. NOTE The addition of PWM-controlled backlight will not break your existing code, the new options have default values, which initialize the used driver to behave as prior to PWM. Only if you want to use the new feature, some changes need to be made. The PWM is configured to be 120Hz (period of 8.33 milliseconds), in order to avoid noticeable flicker in the backlight. If in your opinion this value is too fine, then you can reduce the frequency in the LCD constructor in <lcd_base.cpp> by increasing the period value. My recommendation is to avoid frequencies lower than 60Hz.

2012-12-21¶

• Internal-only changes in the way drivers transmit colors - done to simplify the bitmap drawing routines; client API remains unchanged.

2012-12-12¶

• Added the driver for the ST7735 display controller.
• Added the RGB18 color mode: choose between 16-bit (65K distinct colors) and 18-bit (262K distinct colors) color space [supported by all drivers]. NOTE This feature requires the image drawing functions to be changed, in order to account for differences between configured display color depth and the color depth of the image. Please review the API docs, in particular the new type bitmap_t and the DrawBitmap functions.
• Changed display rotation to be achieved through the correspondent settings in the respective controller registers: no more software translation between width and height in different display orientations.
• Extended the orientation options: PORTRAIT (top line to 12 o'clock/upright) and LANDSCAPE (top line to 9 o'clock) positions are the old options, PORTRAIT_REV (top line to 6 o'clock/upside-down) and LANDSCAPE_REV (top line to 3 o'clock) are the new orientations.
• Added more pre-defined colors: available now are COLOR_BLACK, COLOR_WHITE, COLOR_RED, COLOR_GREEN, COLOR_BLUE, COLOR_CYAN, COLOR_MAGENTA and COLOR_YELLOW.

TODO¶

• Finish implementing PWM-controlled backlight (current-sink configuration).
• Add a driver for the HX8352-A controller (ITDB02-3.2WD 16:9 240x400 pixel resolution display).

How to Use¶

The code is documented, so please review the API docs. There is a simple example to get you started...