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Utilising ARM Cortex-M based SoCs (Part 2)

Posted: 28 Jul 2014 ?? ?Print Version ?Bookmark and Share

Keywords:system-on-chips? ARM? Cortex M? SoC? PSoC?

Using traditional approaches to system design, developers may be given new requirements during any stage of the embedded system development, leading to a complete re-work. While developing a system using a SoC, these risks are reduced substantially as can be seen by examining more closely the gas sensing system example described in Part 1 in this series.

Making changes to an SoC design
In the case of the gas sensing system (figure 8), to make the product competitive in market, the decision was made to utilise a lower cost gas sensor in the design. Now the problem arises that the output current range of this low cost sensor is lower than the previous sensor. To mitigate this problem and achieve the same performance, the system developer decides to add an op-amp in series with the existing TIA. This leads to schematic and PCB re-design when the system developer is following a traditional approach.

Figure 8: Functional block diagram of gas sensing system.

Figure 9: Functional block diagram of gas sensing system after PGA addition.

While using an SoC, the system developer selects the Programmable Gain Amplifier¬¬¬ (PGA) from the component catalogue and places it in the schematic of the SoC IDE.

This additional PGA compensates the reduction in the sensor output current without changing anything on the external circuit or requiring further reworking of the design.

Dealing with market driven design changes
In this scenario, a competitor launches a similar product with better precision into the market. To compete with the new product, it is decided to use a higher resolution ADC. Now the developer has to spend extra time to select a new ADC that matches the new requirements. Developers working with SoC can reconfigure the programmable components to adjust to new requirements.

For example, the ADC component in PSoC Creator provides a large range of configurability to the developer. This can be seen in the component configuration window of PSoC Creator. In our current case, the system developer can change the ADC resolution in the window to resolve the issue quickly with no impact on time to market.

Figure 10: ADC component parameter window.

Increasing the complexity level of an SoC design
Let us now see how ARM-based SoC aids in developing complicated applications such as where interrupt handling, processor efficiency, and instruction execution time play pivotal roles. Key challenges faced are:
???Interrupt Handling
???Memory footprint
???Speed of operation
???Limited hardware resources

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