Direct Drive LCD Design Guide

entire panel to fill with valid pixels is the maximum refresh rate. Displays in existing media systems usually have refresh rates between 48Hz and 120Hz to avoid visible flicker.

HSync, VSync and Dot Clock are all generated using TPU channels of the H8S or H8SX microcontrollers. The TPU allows timer compare actions which synchronize these signals to the ExDMA request line. This ensures that the clocks are generated when valid data is available on the bus.

3.1.5Data Enable

Many panels require an additional signal to frame the valid data – this enable signal is sent at the time the valid data is latched onto the bus – the panel will then clock in the data on the next edge of Dot Clock. It provides added synchronization for the timing of data, but this signal can often be left in the active state if the Dot Clock synchronization to the data is predictable.

3.1.6RGB (Red Green Blue) Data

The data is presented to the panel in parallel. LCD panels have connections for 6 or 8bits of data for each color totaling 18 or 24bits of color resolution. Our solution uses a 16bit data bus, so the most significant bits of the data are presented to the panel. RGB 5-6-5 is the most common 16 bit solution. The least significant bits can be tied low, or better still, to the MSB which would give a slightly improved range over tying to ground.

Specifically with respect to Renesas H8S and H8SX devices, we use the ExDMA module to control the data bus transfers.

3.1.7Touch Screen

Our support is currently for popular resistive touch screen panels which have 4 connections (endpoints of an X axis resistance and Y axis resistance). These inputs provide resistances proportional to the touched location particular X and Y coordinates on the panel.

The host system (microcontroller plus logic) drives the resistive endpoints with a known reference voltage, and the level on the channel is read into an analog to digital converter (ADC). With calibration and scaling in the microcontroller driver code, it is possible to pinpoint the area of the panel that was touched. Action can be taken accordingly.

An example of interface circuitry between the MCU and touch-screen is shown in Figure 6 below.

1

U1A

23

HC126A

4

U1B

56

HC126A

10

U1C

98

HC126A

13

U1D

1211

HC126A

J4

4

3

2

1

MOLEX_52044

R2

1K C1 10nF

R4

1K C2 10nF

R9

1K C4 10nF

R11

1K C5 10nF

TOUCH_YU

R1

DNF

TOUCH_XL

R3

DNF

TOUCH_YL

R8

DNF

TOUCH_XR

R10

DNF

Figure 8 Touch Screen Circuit

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Image 14
Renesas H8SX user manual Data Enable, RGB Red Green Blue Data, Touch Screen
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H8S, H8SX specifications

Renesas H8S and H8SX microcontrollers are part of Renesas Electronics' H-series of 16-bit microcontrollers, widely known for their rich functionality, exceptional performance, and versatility in embedded applications. These microcontrollers are ideal for a variety of applications ranging from automotive systems to industrial automation and consumer electronics.

The key feature of the H8S series is its high-performance CPU architecture, which includes efficient instruction execution, allowing for faster processing of tasks. The H8S series operates at clock speeds typically up to 24 MHz, providing ample processing power for complex applications. The H8SX series builds upon the H8S foundation with enhanced performance capabilities, including advanced instruction sets and support for higher clock frequencies, which can reach up to 40 MHz.

One of the standout characteristics of the H8S and H8SX microcontrollers is their rich peripheral set. They offer multiple I/O ports, timers, ADCs (Analog-to-Digital Converters), and communication interfaces such as SPI, I2C, and UART. The built-in ADCs allow for accurate analog signal processing, making these microcontrollers suitable for measuring temperature, pressure, and other sensor inputs in real time.

Moreover, the H8SX series provides additional features like improved flash memory capacity, enabling more complex applications to be developed and more extensive firmware to be stored. With the integration of a high-performance interrupt controller, the H8SX models can manage multiple interrupt sources efficiently, allowing for real-time response to events.

The H8S and H8SX microcontrollers also support a variety of development environments and programming languages, making them accessible for developers with varying skill levels. They are compatible with both C and assembly language programming, along with a range of development tools and IDEs (Integrated Development Environments).

In terms of power consumption, these microcontrollers are designed to be energy-efficient, making them ideal for battery-operated devices. With features such as low-power modes that allow the device to enter sleep modes when inactive, the H8S and H8SX microcontrollers help extend the battery life of applications.

In summary, Renesas H8S and H8SX microcontrollers stand out due to their performance, extensive peripheral functionality, versatility, and energy efficiency. Their rich feature set and compatibility with a variety of development tools make them a desirable choice for developers looking to create innovative embedded solutions across multiple industries.
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