The number of development platforms for building hardware support platforms for the Apple iPhone and iPod is probably not surprising given the popularity of these consumer devices. But what is impressive is how quickly new products can be created using these new platforms.
Cypress Semiconductor’s platform brings its line of PSoC processors to the party (see “Field-Programmable I/O Augments 8- And 32-Bit Microcontrollers”). Microchip’s platform also brings a range of 8- to 32-bit products to the mix. Finally, XMOS targets the iPhone and iPod with its platform based on its event-driven XS1-L1 processor.
These development platforms take advantage of Apple’s OS 3. This version of the operating system is designed to integrate with external accessories via the Bluetooth 30-pin connector. External devices can provide a range of features such as more sophisticated and powerful audio processing and delivery.
PSoC MEETS THE iPHONE
Cypress Semiconductor’s Made for iPhone and iPod (MFi) CY8CKIT-023: PSoC Expansion Board (Fig. 1) initially targets the 8051-based PSoC line. Support for the original PSoC 1 and the 32-bit ARM-based PSoC 5 is in the works. All three introduce the configurable digital and analog peripheral subsystem to the process.
The CY8CKIT-023: PSoC Expansion Board holds the iPhone interface and support circuitry. The PSoC 3 DVK host board has the PSoC 3 processor. The DVK has four expansion sockets. Only one is needed for the iPhone interface. The others can be used with a range of boards from Cypress such as the CapSense touch interface.
Cypress Semiconductor’s MFi external accessory software framework sits between the application stack and PSoC functions such as the CapSense support as well as services such as battery management and LCD display drivers. The software works with the company’s PSoC Creater. This integrated development environment (IDE) is also used to configure the digital and analog subsystems. Significant reductions in bill-of-materials (BOM) are possible using custom configured on-chip peripherals.
PIC AND iPHONE
Microchip has delivered three different platforms including one for the 8-bit PIC line (Fig. 2). Another addresses Microchip’s higher-performance 16- and 32-bit line of microcontrollers and digital signal controllers. The third is a digital audio development platform for the iPhone and iPod.
The first two platforms take Cypress Semiconductor’s approach, using an existing host board and attaching the iPhone or iPod using an interface board. This reduces costs and allows existing tools to be employed. It also includes the ability to swap out processors. Microchip delivers its processors on small square modules that plug into the host board.
Microchip’s MPLAB IDE development tool suite works with these platforms. Support includes a no-cost runtime library for supporting the iPhone and iPods. It also supports features such as battery charge management.
EVENT DRIVEN iPHONE
The XMOS 185 MIPS XS1-L1 processor chip (Fig. 3) costs $5 but brings a significant amount of compute horsepower to the table. Its reference design platform is designed for digital processing and even full digital delivery of audio. This includes connections for I2S, S/PDIF, and a class D amplifier.
High-performance digital processing is a compute hog, but it delivers excellent results. The 32-bit XMOS processor tackles the problem using a 64-bit media access controller (MAC) to reduce bit errors. Its asynchronous clock architecture eliminates clock jitter issues.
The system can still drive analog outputs, but the digital support provides superior audio. It also boasts superior noise immunity. Likewise, the audio fidelity is under complete digital control of the designer, eliminating analog design issues. The all-digital approach makes it significantly easier to add and remove audio processing features as well.
Don’t rush out too quickly, though. Developers do need to be an Apple licensee to get the secret sauce needed to communicate with the iPhone and iPod.