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Designing cost-effective 3D using SoC

Posted: 09 Aug 2011     Print Version  Bookmark and Share

Keywords:3D  SoC  active shutter 

Another area designers are considering is a move to more configurable microcontrollers with fixed function analogue capabilities. These microcontrollers work well because they are able to provide a wide range of configurability options versus an ASIC-based solution. Despite the increase in analogue capabilities, most microcontrollers still have limited internal resources. Although many devices contain some fixed internal peripherals such as ADCs, comparators, timers, and PWMs, they lack many other key components that are required in a 3D glasses design. While the configuration options are great, the integration options are limited.

To help compensate for the limited integration, many companies adopt an IR module to handle the IR receiver. This module contains all the required components to receive, amplify, and filter the IR synchronisation signal in a small and simplistic package. The issue with the module is it contains fixed specifications and does not allow manufacturers to tweak or modify the module as they see fit. These limitations also require decoding of the IR synchronisation to be handled with assistance of the CPU, increasing the power consumption of the device. This methodology may also reduce the performance of the CPU when working on other tasks because of the time critical nature of decoding the synchronisation signal, which is dependent on how often synchronisation is required.

The limitations of both the ASIC-based and microcontroller-based architectures force device manufacturers to choose between configurability and integration. This trade-off also makes it difficult to implement a true universal design as discussed in the previous section.

Programmable SoC
The Consumer Electronics Association (CEA) is working on a standardisation of the IR synchronisation protocol for 3D glasses. However, until this standard is finalized and adopted by the television manufacturers, designing a universal pair of 3D glasses to operate with all major television brands will require a significant amount of effort in terms of component count and design time. Each television manufacture will have a different requirement for the IR frequency, filtering requirements, and IR protocol.

The challenge is to be able to detect which television manufacturer the viewer is using and dynamically adjust the 3D glasses to support that television's various requirements. This is where System on Chip (SoC) devices will play an essential role in the universal 3D glasses market. They provide the ability to migrate from the traditional fixed function device to fully configurable devices. These SoC devices include a wealth of programmable digital and analogue resources that are capable of being adjusted dynamically. Upon powering of the SoC device, the analogue and digital peripherals can reconfigure as they scan the IR signal until the device acquires a match on a television manufacturer. The device can then fully adjust the programming and operation to match the manufacturer's specifications, functioning just as a pair of glasses produced by that manufacturer would.

Many of these SoC devices include analogue peripherals such as filters, amplifiers, demodulators, and comparators. These peripherals remove the need for an elaborate external analogue front end. Since these analogue peripherals are internal to the device, register adjustments are all that is required to change the gain, filter parameters, and threshold levels. Digital peripherals such as timers/counters, PLDs, and various communication protocols, can also be adjusted dynamically to suite the protocol decoding and shutter control requirements.

The analogue and digital capabilities of these SoC devices also allow the battery charger and the high voltage shutter control to be implemented in a single device, leaving only passive components externally, such as FETs, inductors, capacitors, diodes, etc. This also allows the design to be transferred to different pairs of glasses with

minimal design changes. Adjusting a few parameters in firmware, the boost output voltage for the shutters can be modified without changing the external hardware. As the battery capacity changes, a few adjustments in firmware can accommodate the new battery without modifying the external circuit. Finally, with majority of the display synchronisation front end implemented internally in the device, the external schematic remains untouched while the internal peripherals are adjusted in firmware.

PSoC 3 family of devices from Cypress Semiconductor are touted to have the ability to implement the majority of 3D glasses functionality internally. These devices include programmable analogue routing and functional blocks for analogue peripherals, PLD logic to create digital peripherals, and a high speed Intel 8051 core. These devices also contain an internal digital filter block that can be used to implement dynamic adjustments of the IR filtering requirements depending on the design.

In the end, moving from the discrete or ASIC based solutions of today to more flexible system on chip solutions now being offered, provide significant advantages for both designers and consumers.

- Tyson Lunsford
  Business Development Manager
  Cypress Semiconductor


  Robert Murphy
  Application Engineer
  Cypress Semiconductor

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