Atmel has launched its first family of microcontrollers based on ARM's Cortex M0+ core that introduce several features designed to streamline PCB design as well as a configurable serial-port controller.
The SAMD20 family is designed to offer a 32bit migration path for users of the company's existing AVR 8bit architecture, carrying over the peripheral controllers and Sleepwalking system that Atmel provides on those parts, as well as existing higher-end ARM parts, that are designed to let the processor core sleep for longer and work with more I/O intensive applications.
"When we did customer research for XMega, the CPU bandwidth was not their bottleneck, it was in the peripherals. So we invented the Peripheral Event System," said Andreas Eieland, senior product marketing manager for Atmel. "Then Sleepwalking was built on top of that system. With Sleepwalking, you can tell the A/D converter if the read value is below a threshold that it can return to sleep until the next value needs to be taken. But if above the threshold, it can trigger an interrupt to wake up the CPU.
"For Sleepwalking, one thing we have added that we didn’t have before in the lower-end devices is the ability to have a PWM running in deep-sleep mode."
In the peripheral system, the main change is a programmable serial controller designed to make it easier to configure each UART to a specific role rather than providing fixed I2C or SPI ports. "There are multiple instances of the SerCom on each device. Also, the pins are spread out around the package. You can choose the pinout on the package to save real estate on the PCB. One customer was able to remove a layer on their PCB with this feature," Eieland claimed.
"The devices are made to be upward compatible with the M4-based devices. Also, the analog pins are all on the bottom side. Even if you move from one layout to another the impact to the PCB is minimal. With a TQFP you can lay out the packages inside each other, make it possible to reuse designs from one project in another or if you change your mind on the current design," Eieland added.
"The last piece of the puzzle is what we get from Cambridge. One of the huge benefits of the M0+ is that it has single-cycle I/O access. A lot of systems still use ‘bit banging’ I/O: this provides deterministic I/O access, which is vital for that style of programming," Eieland explained.