As you may recall, Energy Micro is an Oslo, Norway, provider of energy friendly microcontrollers and RF transceivers based on ARM Cortex processor cores. Silicon Labs, which acquired Energy Micro this year, today announced the EFM32 Zero Gecko MCU family. This means that Silicon Labs/Energy Micro now offers more than 240 scalable EFM32 Gecko Microcontroller options.
You have to love the names. Members of the Zero Gecko family (the focus of this column) are based on the ARM Cortex-M0+ processor. Members of the Tiny, Gecko, Leopard, and Giant families are based on the Cortex-M3. Members of the Wonder family are based on the Cortex-M4.
Just in case you were wondering, EFM stands for "Energy Friendly Microcontrollers." Also, the Cortex-M0+ is a relatively minor upgrade to the Cortex-M0. It fixes a couple of niggles and offers better energy efficiency.
A lot of designers of products traditionally based on eight-bit and 16-bit microcontrollers featuring proprietary architectures are looking to move into the 32-bit world. The Zero Gecko family offers an ideal solution for a wide range of low-power and battery-powered applications, including mobile health and fitness products, smart watches, activity trackers, smart meters, security systems, and wireless sensor nodes. They are also ideal for batteryless systems powered by harvested energy.
In addition to a range of best-in-class analog peripherals, including an on-chip current digital-to-analog converter, Energy Micro said, the Zero Gecko is the only Cortex-M0+ based chip on the market with energy-efficient AES encryption in hardware.
As illustrated in the block diagram below, the Zero Gecko's Cortex-M0+ includes a DMA controller (not always the case with low-cost devices). The Zero Gecko also offers very sophisticated clock management, including high- and low-frequency crystal oscillators and high-, low-, and ultra-low-frequency RC oscillators. Different clocking systems are better suited to different applications and/or different tasks within the same application. The chip can switch between any of these clocking alternatives on the fly.
EFM32 Zero Gecko Block Diagram (click here for a larger version).
For serial interfaces, in addition to I2C and a regular universal synchronous/asynchronous receiver transmitter, the Zero Gecko offers a low-energy UART. It features five energy modes:
- EM0 Run Mode: 110µA/MHz
- EM1 Sleep Mode: 50µA/MHz
- EM2 Deep Sleep Mode: 900nA (RTC, brownout detection, RAM and CPU states retailed)
- EM3 Stop Mode: 510nA (brownout detection, RAM and CPU states retailed)
- EM4 Shutoff Mode: <20nA (Pin/GPIO reset)
Silicon Labs says the Zero Gecko can wake up from its low-power modes into its running mode in only 2µS while competitive offerings can take anywhere from 4µS to 200+µS. It also says that the current values it quotes are realistic values based on real use scenarios. For example, the value of 110µA/MHz shown above is while running at 24MHz executing real code evaluating a prime number algorithm running out of Flash memory. This is not silly code whose only purpose is to provide unrealistic, artificial results.
One area of particular interest for ultra-low-power operation is the Zero Gecko's ability to provide the maximum amount of functionality while in its sleep, stop, or shutoff modes. This is achieved by having intelligent peripherals that can talk directly to one another without waking the CPU (when it's running, the CPU is the dominant factor with regard to battery life). For example, the designer might set things up so that, when a timer or an analog comparator trips, the analog-to-digital converter performs a conversion, and then the direct memory access (DMA) unit can store the value in memory, all while leaving the CPU happily snoozing away.
The 16 members of the Zero Gecko family have Flash memory sizes ranging from 4 to 32Kbytes, up to 37 GPIOs, and QFN24, QFN32, and QFP48 package options. Samples of the Zero Gecko MCU family are available now. Production quantities are planned for this quarter, and pricing begins at $0.49 in 100K quantities.
Last but not least, Silicon Labs is also announcing the availability of an all-inclusive, cost-effective starter kit called the EFM32ZG-STK3200 to accelerate evaluation and application development for Zero Gecko-based products.
Featuring an advanced energy monitoring system (no need for a multimeter or oscilloscope), memory, capacitive touch buttons, and an LCD, along with a built-in SEGGER J-Link that reduces the need for debug dongles and saves cost, the EFM32ZG-STK3200 is economically prices at $69.