Originally designed for use in the PC industry, the Universal Serial Bus (USB) is rapidly finding an even bigger market in the embedded world. There, USB connectors are taking up residence on microcontrollers and being incorporated into devices ranging from motor controllers to joysticks to thumb drives.
USB is relatively cheap and relatively straight forward, says Terry West, director of marketing for the High-Performance Microcontroller Div. at Microchip Technology Inc. It's already ubiquitous on every PC, so it's obvious to say that we should be putting USB devices on our chips.
Microchip says USB devices are finding use among all kinds of embedded product manufacturers. An Asian scale manufacturer, for example, incorporated a Microchip USB-enabled microcontroller on its scales, enabling them to be connected to cash registers and printers.
Moreover, the new breed of USB-based microcontrollers is eliminating the need for ASICs and therefore driving down the costs of USB functionality on such low-cost devices as keyboards and PC mice.
Here, we've included information on recently released USB-capable microcontrollers from Microchip, Texas Instruments and Atmel. This group includes 8-, 16- and 32-bit products, providing a good starting point for designers working on a wide variety of embedded products.
Microchip's USB Microcontroller Family
Announced in June, Microchip Technology's 8-, 16- and 32-bit USB microcontrollers deliver USB functionality to a broad variety of products ranging from thumb drives to medical instruments. They support the USB 2.0 Device and provide an easy migration path using a single integrated development environment (IDE), known as MPLAB IDE. The growing portfolio of devices includes the 16-bit PIC24F USB family, which is pin-, peripheral- and software-compatible with the new 80-MHz, 32-bit PIC32 USB MCUs. Microchip is also expanding its 8-bit USB product offering with the lower-cost, smaller-footprint PIC18F1XK50 family. All the products are supported by free USB software stacks and drivers.
TI's Ultra-Low-Power MCU Offers USB Capability
Texas Instruments' MSP430 microcontrollers combine ultra-low power consumption with 25-MHz peak performance and integrated peripherals, such as USB. With active power consumption as low as 160 ΅A/MHz and standby power consumption 1.5 ΅A, the MSP430F5xx enables longer battery life and the ability to use smaller batteries for portable applications. It also offers the possibility of using no batteries at all for energy harvesting systems that run off solar power, vibration energy or human body temperature.
Atmel's USB Microcontrollers
Atmel's AVR microcontrollers combine a USB controller with high-performance analog features. Targeted at gaming peripherals, low-cost motor control and sophisticated joysticks, the ATmega16U4 and ATmega32U4 combine optimized battery charging with USB functionality. They incorporate a feature set aimed at applications requiring a number of A/D conversion channels and several PWM channels. They also include hardware flow control on the USART, which eases the connection to other devices when bridging with USB at high baud rates.