Comparing PSoCs and MCUs in digital TV design
Designing a Digital TV with PSoCs
In rethinking the design of a digital TV, the embedded developer can take advantage of the fact that a PSoC is a combination of a microcontroller with programmable logic and high performance analog to digital conversions and commonly used fixed-function peripherals. Available as an 8-, 16-, and 32-bit MCU, it has Flash memory up to 64KB, SRAM up to 8KB, and internal EEPROM up to 2KB.
Particularly useful in digital TV designs, a PSoC has internal configurable delta-sigma ADC with 8- to 20-bit resolution, 8-bit DAC, four 16-bit configurable timers, four 16- bit PWMs, Clock, Multiplexer, Comparators and I2C. Also useful is the fact that a PSoC operates in an ultra low power mode consuming <1 µA current, which can be used to allow a user to operate the digital television in standby mode.
PSoC has an internal PGA, comparators, and configurable delta-sigma ADC with 8- to 20-bit resolution and sample rates up to 192ksps. It is used to measure different analog inputs (for example, a light sensor, temperature sensor, humidity sensor, etc.) For example, a light sensor interface in a TV application is useful for auto adjusting the TV monitor’s brightness and contrast based on the ambient room light.
PSoCs can directly drive LED and LCD displays (Segment LCD, Graphic LCD and Character LCD displays) for displaying channel and volume information on the front panel. PSoC has an operating range of 1.71V to 5.5V so it can be easily interface with external peripherals for other applications. PSoC can also directly drive on-board relays, which is helpful for the power supply in standby operation.
PSoCs have an internal RTC component for real time measurement, as well as an internal system clock that does not requires external clock/oscillator circuitry. PSoCs also supports the USB 2.0 interface, enabling users to interface external memory (Hard disk) containing audio and video files to the TV. Additionally, PSoC supports the Secure Digital (SD) card interface for audio and video storage as well.
Using the PSoC Creator IDE tool, all the interface and logic can be designed. PSoC Creator has readily-available component blocks for designing interfaces and logic like SARADC and PGA for analog sensors and other signal inputs, as well as other components like I2C, SPI, IR Receiver, PWM, CLK, MUX, TIMERS, USB and CMP for Digital TV application.
PSoC Creator also enables user to tap into an entire tools ecosystem with integrated compiler tool chains, RTOS solutions, and production programmers. With PSoC Creator, developers can create and share user-defined, custom peripherals using a hierarchical schematic design. They can also automatically place and route select components and integrate simple glue logic, normally located in discrete multiplexers.
PSoC supports capacitive sensing technology that replaces mechanical buttons on the keypad. PSoC supports sliders for volume up/down functionality. PSoC also supports proximity sening for the front keypad, enabling the front keypad to be activated once the user places a hand near the keypad (i.e., the TV will react to the hand movements, so that user can change the channels).
PSoC has internal 8-bit DAC, which will be used for controlling volume of the speaker and also performs the mute function for the audio speaker. An internal DAC on the PSoC will also used for controlling brightness and color quality of video output by varying the gain of the video amplifier.
RF and microcontroller-based mixed-signal board design is needed to meet audio and video performance requirements. PSoC is a combination of a microcontroller with programmable logic and high performance ADC capabilities. As shown in Figure 4, below, using a PSoC in a design will improve board performance by using internal programmable analog and digital peripherals. Filter implementations using PSoC will also improve the signal quality and help cancel system noise.
Click on image to enlarge.
Digital televisions need a low-cost front panel design with different features like buttons, LEDs and smartcard interfaces. PSoC supports capacitive sensing technology to enable sliders and proximity sensing to be implemented in the front panel design. Meeting signal to noise (SNR) performance with nearby LEDs (PWM-based) on a front panel is a design challenge for system designers.
Current digital TV designs: what could be improved
PSoCs support capacitive sensing technology to replace mechanical buttons with capacitive-based keypads. It also reduces failure due to mechanical buttons and provide better product reliability. PSoC Creator supports CapSense SmartSense components which autotunes the sensitivity of CapSense buttons. Implementation of touch screen based design on the front panel instead of LCD display and keypad will provide better user interface and flexibility.
PSoCs support SPDIF (Sony/Philips Digital Interface) and MIDI (Musical Instrument Digital Interface) components in PSoC Creator, It will help user to interface with other external audio devices and instruments.
Currently the TV application is based on a single-tuner. With a double-tuner based design (Cable and satellite Tuners), users can view two pictures in Picture-in-picture (PIP) mode. With an interface for external devices like iPod / iPhone, the system can communicate to the media devices across the UART or USB ports. User can interface iPod / iPhone devices for different audio and video applications.
Ronak Desai is a Staff Engineer at Cypress Semiconductor with nine years of industry experience. He hass a BE in Electronics and Communication from Mumbai University, India. He is part of the Development Kits Group and is based out of Bangalore, India. You can reach Ronak at rkad@cypress.com.
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