Building XMEGA-based energy harvesting RF sensor nodes

An energy harvesting RF sensor node is a device powered by various environmental means including solar, thermal (heat/cold) and even vibration. RF sensor nodes are typically used to monitor environmental changes such as temperature, pressure and ambient light – with data transmitted via RF to a host for remote sensing and control.

Energy harvesting RF sensor nodes are routinely deployed by manufacturers of building automation, climate control, access control and other self-powered sensor networks. Key design considerations include ultra-low power and low operating voltage, the (potential) expansion of such technology into a broader range of applications and high precision analog peripherals.

The following Atmel components can be used to design an energy harvesting RF sensor node that meets the above-mentioned industry requirements: Atmel’s ATxmega D or E series, AT86RF231/232/233 RF transceiver and AT30TSE Serial EEPROM with temperature sensor.

“Atmel’s AVR XMEGA D/E series and 86RF23x series offer low power consumption and true 1.62V operation, addressing the key design requirements for energy harvesting RF sensor nodes,” an Atmel engineering rep told Bits & Pieces. “Atmel’s XMEGA D/E series also boasts true 1.62V-3.6V operation, 5 sleep modes with fast wake up time, < 1uA in Power Save mode (RTC), 190uA/MHz at 1.8V in active mode, along with an Event system and Peripheral DMA Controller to further offload CPU activity.”

Atmel’s 86RF23x series is also capable of maintaining a sleep current consumption of < 20nA, along with a current consumption as low as 6.0mA RX and 13.8mA TX. As expected, the 86RF23x series is supported by Atmel’s complete line of IEEE 802.15.4-compliant protocols for low power applications: IPv6/6LoWPAN, ZigBee, 802.15.4 MAC and lightweight mesh network stack.

On the software and development side, engineers designing XMEGA-based energy harvesting RF sensor nodes can take full advantage of Studio 6 and Atmel Software Framework (ASF), ASF high-level drivers for sensors and wireless interfaces, as well as Atmel’s comprehensive portfolio of Xplained kits.

Interested in learning more about building XMEGA-based energy harvesting RF sensor nodes? Be sure to check out some of the links below:

• Atmel AVR XMEGA family home page
• Atmel AT86RF231/232/233 RF Transceiver Home Page
• Atmel AT30TSE Temp Sensor Home Page 
• Atmel MCU Xplained Kits Home Page
• Atmel Studio 6 Home Page

Designing an advanced glucose meter with AVR MCUs

A glucose meter can best be described as a portable battery powered medical device used to measure blood glucose concentration on test strips.

Glucose meters are typically equipped with a display and mass storage solution, with certain models featuring an IrDA or a USB interface to export data to a computer. Unsurprisingly, there is currently an emerging trend for glucose meters to be equipped with Bluetooth or BTLE capabilities, thereby facilitating easy connection to mobile devices such as smartphones and tablets.

Key design considerations for a glucose meter include ultra low power consumption, high system integration (high-end analog peripherals), low BOM cost and versatile connectivity options for bio-sensors, display, buzzer, memory and PCs.

As illustrated in the diagram above, Atmel’s versatile AVR portfolio can be used to help engineers design an advanced glucose meter using the ATxmega256A3BU 8/16bit low power AVR-based MCU, AT86RF231/232/233 RF Transceiver, AT42QT Touch IC and ATSHA204 Authentication IC with EEPROM.

“Simply put, Atmel’s ATxmega256A3BU offers ultra low power consumption, high integration, compact package and connectivity features to address the key needs of a glucose meter,” an Atmel engineering rep told Bits & Pieces.

“In terms of ultra low power requirements, our ATxmega256A3BU supports 1.62-3.6V and boasts 5 flexible sleep modes. In Power Save mode (RTC running), the current consumption is below 1uA, while in Active Mode, the current consumption is 350uA/MHz at 1.8V. Meanwhile, a DMA Controller handles data transfer between the peripherals and memory.”

On the connectivity side, Atmel offers a full speed compliant USB device port with embedded PHY to save BOM cost (~$0.5-$1.0). As expected, the port can be used for battery charging and data transfer to a PC. Atmel also offers integrated UART, USART, SPI and I2C – allowing easy connection to external sensors, memories and display.

“It should also be noted that Atmel-powered glucose meters require a minimum in terms of external (additional) hardware, thanks to integrated RTC, high performance ADC and DAC, PLL and voltage reference,” said the engineering rep.

“And last, but certainly not least, Atmel’s AVR MCUs benefit from our extensive software ecosystem, such as Atmel Studio and free software libraries of production ready source code including ZigBee PRO Software (BitCloud), Proprietary Low Footprint, 802.15.4 Mesh Software Stack, USB Stack and QTouch Library.”