Frequently Asked Questions
Frequently Asked Questions
- What is the process for designing a custom LCD?
Please see our infographic on designing a custom LCD.
- What does the viewing angle of a display specify?
The viewing angle specifies the angle at which the display is best viewed from. Different viewing angles can affect apparent contrast and visibility of the screen. The viewing angle can depend on LCD fluid type and duty cycle.
- What is the temperature range of my display?
The temperature range is specified for each display and can range from normal, wide to ultra-wide. The specific temperature range of the display is listed as an operational temperature and storage temperature in the datasheet of the display. For example, the wide temperature range is from -20 to 70 ˚C.
- What unit is display brightness measured in?
Display brightness is specified in terms of nits or candelas per square meter (cd/). This is the measurement of light emitted from the display per square meter. 1 cd/m2 is the brightness of an average candle.
- How is backlight power specified?
The backlight power is specified as the forward voltage and current applied across the entire backlight circuit not per LED. If the forward voltage and current is supplied to the anode and cathode pins of the backlight the LEDs will turn on.
- What is the difference between active area and viewing area?
The viewing area is the area of the glass on the display. The active area is the the area in which the pixels can be displayed.
- What is CGRAM?
CGRAM is an acronym that stands for “Character Generated RAM” which is a memory location provided by the display for character generation. This memory defines the available characters and has a small amount of memory for custom character generation for character LCDs.
- What is DDRAM?
DDRAM stands for “Display Data RAM” which is the memory location that references the pixels to be displayed. This memory location acts as a working data buffer for the display. The DDRAM controls which character/bitmap is displayed.
- What is an IPS display?
IPS stands for “In Plane Switching” which is a display technology that differs from TN, VA and OLED. IPS displays have features such as improved contrast, wide viewing angles, faster response times and higher color consistency.
- What does it mean for a transmissive display to be “normally black” or “normally white”?
The normally black description refers to TN displays that block the backlight when the pixels are not in use. This means the display will have a default black screen. A normally white mode display allows the backlight to shine through the TN and will have a default white screen.
- What is the refresh rate should I operate my display at?
The refresh rate is how often the display is refreshed per second in order to maintain an image. A display is typically refreshed, or redrawn, at a rate of 60 frames per second or 60 Hz.
- What is a Sunlight Readable display?
A Sunlight Readable TFT is an LCD that has a high-powered backlight to illuminate images at high brightness which allows the image to be visible in direct sunlight. A display must have a brightness of 700 nits or higher to be considered sunlight readable.
- What are 666 mode and 565 mode?
These reference the interface pixel format command for the display. 565= 5bits Red, 6bits Green and 5bits Blue (65k colors & 16-bits per pixel) and 666=six bits for each color (262k colors & 18-bits per pixel). The mode is set in the initialization sequence of the code. The command and data code is the same for both ILI9488 and ST7796 controllers.
write_command(0x3A); //Interface Pixel Format
write_data(0x05); //for 565RGB or change to 0x06 for 666RGB
- How do I calculate the power consumption of a segment LCD without an IC?
A rough estimate for the power consumption of a segment LCD is 1.5uA/cm2 of active segment area.
- How close can segments be drawn on an LCD?
Assuming there are no traces running between the segments, the segments will require a minimum of 0.2mm spacing between them. Please contact Focus LCDs to determine if traces will need to be routed between segments and confirm spacing of segments.
- Can an overlay be used with a resistive touch screen?
Yes. It is recommended that an overlay used with a resistive touch screen is no more than 0.25mm thick and consists of a polycarbonate or polyethylene material.
- What is the best way to mount my TFT?
Our recommended mounting method can be found here.