Tag Archives: ZigBee Pro

ATmega256RFR2 powers low-cost Ethernet to wireless gateways: Part 3

Earlier this week, Bits & Pieces introduced Atmel’s low-cost gateway (LCGW) reference design, powered by the versatile ATmega256RFR2 and WIZnet W5200. We explored the basics of the platform, including operation and CPU functions. We also took a closer look at the W5200 chip, memory, power system and antennae. Today, we will be diving into possible LCGW enclosures, regulatory compliance, debugging and software resources.

As we all know, users can be very creative with their enclosure designs. However, there are some basic guidelines for wireless devices. Perhaps most importantly, any metal or conductive material within 4 inches (10cm) of the antenna will have an effect on the far field radiation pattern. As such, metal enclosures should not be used. It is also recommended to keep metal parts such as screws, nuts and washers, metallic labels away from the PCB antenna area. Indeed, there are holes in the LCGW design which act as the preferred location for non-conductive fasteners.


In terms of regulatory compliance, the LCGW has been pre-tested for FCC Class B and CE compliance. Initial pre-scan data indicates this design is compliant with US and EU regulations. To obtain regulatory certification, developers will have to perform regulatory testing of their product in its final form – including enclosure and all application specific features. Although results may vary, the positive pre-scan results are reassuring and indicate the probability of successful certification is high.

The Atmel ATmega256RFR2 SoC used in the LCGW has a special Band-edge filter feature, which improves out-of-band rejection for channels 25 and 26 (2475 and 2480MHz.) The FCC defines a “Restricted Band” from 2483 to 2500MHz, meaning emissions in this Restricted Band are required to be below 54dBµV (500µV/m). Because of this requirement, many IEEE 802.15.4 devices are not able to use high power in channels 25 and 26. Nevertheless, the Band-edge filter feature of Atmel RFR2 radios allows the use of higher power in these channels. It should be noted that the FCC pre-scan data cited in this Bits & Pieces article was taken using the full output power of the  ATmega256RFR2  (+3.5dBm) and the Band-Edge feature enabled. The filer can be enabled by setting PLL_TX_FLT (bit 4) in the TRX_CTRL_1 (0x144) register.

On the debugging side, the DCP power inlet is fused for safety purposes. So if the Power-Good LED fails to light, be sure to check the fuse. If the fuse has blown and needs to be replaced, the root cause should be determined before putting the device back into service. For replacement parts, a 1 Amp 0603 SMT fuse is recommended (Bourns SF-0603S100, or equivalent). Do not use flipped CAT5 cables and be sure to exercise caution when connecting to Power Test Header J5, as this header exposes 5VDC and may damage low voltage GPIO or UART cables.

Although leveraging the 3.3V supply for light external loads is permissible, be advised that the 3.3V LDO has limitations on available line current, load current and thermal dissipation, so exceeding these limits may cause a malfunction. However, at maximum transmitter power, the Atmel  ATmega256RFR2  may exceed emissions limits in the 2483 to 2500MHz restricted band. This can be corrected by enabling the PLL_TX_FLT bit in the TRX_CTRL_1 register. Note – this special bandedge filtering feature of the Atmel RFR2 family allows use of high-power in channels 25 and 26.

Last, but certainly not least, Atmel supplies many network stacks that run on the ATmega256RFR2  These include the BitCloud ZigBee stacks, ZigBee Pro, ZigBee Light Link and ZigBee Home Automation, IEEE 802.15.4 MAC and the Atmel proprietary Light-Weight Mesh network stack.

Interested in learning more about Atmel’s low-cost gateway (LCGW) reference design? Be sure to check out part one  and two of this series.

Cooking with Atmel MCUs

Did you know that some scientists believe the advent of cooking played an important role in human evolution? Indeed, most anthropologists theorize that cooking fires first developed around 250,000 years ago, with the rise of agriculture, commerce and transportation between civilizations in different regions offering cooks many new ingredients.

Clearly, we’ve come a long way since the days when humans roasted meat on a spit over an open fire without any utensils, appliances or kitchens to be seen. Today, however, cooking appliances such as stoves, microwave ovens and conventional ovens typically require a combination of temperature and mass sensors, programmable timers and sophisticated motor control for relevant components. A number of current-gen units include remote controls, as well as rich, responsive touch control interfaces which are key for ease of use.

Now we’ve discussed quite a number of use cases for Atmel MCUs over the past few days, including automotive, lighting, telecare and even washing machines. So it shouldn’t come as much surprise to readers of Bits & Pieces that Atmel also offers a lineup of touch solutions and customizable microcontrollers which are ideal to power a wide range of cooking appliances.

Indeed, AVR microcontrollers are available in 105°C versions, as well as models up to 150°C, which are perfect for high temperature cooking requirements. Plus, Atmel offers a wide range of 8- and 32-bit microcontrollers dedicated to motor control – providing support for BLDC motors, AC motors and switched reluctance motors.

AVR 32-bit microcontrollers also feature a multi-layer databus and DMA controller that make them a perfect fit for HMI applications where high bandwidth is required. Meanwhile, robust touch sensor technology, coupled with Atmel’s QTouch library, allows designers to add capacitive touch buttons, sliders and wheels – without additional cost.


In addition, native 5 volts support is available on the Atmel megaAVR and Atmel tinyAVR microcontrollers (MCUs), with high integration solutions, such as motor control and HMI touch in a single-chip, helping to reduce BOM. ZigBee PRO compatibility enables standards-compliant connectivity and smart metering, with node authentication capability supports smart meter infrastructure connections.

And last, but certainly not least, Atmel’s QMatrix technology offers a robust method to implement buttons and sliders in capacitive touch-technology, while built-in support for water rejection makes the QTouch solutions ideal for demanding environments.

Interested in learning more? Additional information about Atmel MCUs targeting various cooking appliances can be found here.

Putting Atmel AVR MCUs in your refrigerator

Power efficiency is an obvious, yet critical element of refrigeration design. To meet current green energy requirements, refrigerators and freezers are required to include support for global efficiency standards, as well as advanced communication capabilities for smart metering.

AVR MCUs can be used to provide flexible connectivity options and power efficient architectures that make them an excellent fit for refrigeration applications. Indeed, a variety of 8- and 32-bit Atmel microcontrollers are specifically optimized for motor control – providing full support for BLDC motors, AC motors and switched reluctance motors. As an added bonus, Atmel solutions meet energy efficiency requirements such as Energy Star and European regulations to deliver maximum efficiency.

“Atmel AVR 32-bit microcontrollers feature a multi-layer databus and DMA controller that make them a perfect fit for HMI applications where high bandwidth is required,” an engineering rep told Bits & Pieces.

“Robust touch sensor technology, featuring the Atmel QTouch library, allows designers to easily add capacitive touch buttons, wheels and sliders at no additional cost. Meanwhile, native 5 volts support is available on the Atmel megaAVR and Atmel tinyAVR microcontrollers, with node authentication capability supporting smart meter infrastructure connections. And last, but certainly not least, ZigBee Pro compatibility enables standards-compliant connectivity and smart metering.”

Refrigerators are an N1 energy consumer – understandably requiring power-efficient technology. In short, Atmel microcontrollers and wireless products are a perfect fit to help engineers design related products with granular energy control and optimized efficiency.

Interested in learning more? Additional information about the use of Atmel MCUs in refrigeration design can be found here.