原标题：Atmel ATSAMR21LED驱动器参考设计

　　Atmel公司的ATSAMR21是采用32位ARM®Cortex®-M0+处理器的低功耗微控制器,集成了超低功耗2.4GHz ISM频段收发器,256KB闪存,32KB SRAM,最大工作频率48MHz,达到2.46 Coremark/MHz,工作频率1.8V – 3.6V,主要用在ZigBee照明.本文介绍了SAM R21主要特性,MCU框图和内部连接图,以及具有ZigBee光连接的ATSAMR21 LED驱动器AT13518主要特性,电路图和材料清单,PCB设计图.

　　The Atmel® | SMART™ SAM R21 is a series of low-power microcontrollers using the 32-bit ARM®Cortex®-M0+ processor and an integrated ultra-low power 2.4GHz ISM band transceiver. SAMR21 devices are available in 32- and 48-pin packages with up to 256KB Flash, 32KB of SRAMand are operating at a maximum frequency of 48MHz and reach 2.46 Coremark/MHz. They aredesigned for simple and intuitive migration with identical peripheral modules, hex compatiblecode, identical linear address map and pin compatible migration paths between all devices in theproduct series. All devices include intelligent and flexible peripherals, Atmel Event System forinter-peripheral signaling, and support for capacitive touch button, slider and wheel userinterfaces.

　　The Atmel SAM R21 devices provide the following features: In-system programmable Flash,optional 512KB serial Flash,12-channel direct memory access (DMA) controller, 12-channelEvent System, programmable interrupt controller, up to 28 programmable I/O pins, ultra-lowpower 2.4GHz ISM band transceiver with a data rate of 250kb/s, 32-bit real-time clock andcalendar, three 16-bit Timer/Counters (TC) and three 16-bit Timer/Counters for Control (TCC),where each TC can be configured to perform frequency and waveform generation, accurateprogram execution timing or input capture with time and frequency measurement of digitalsignals. The TCs can operate in 8- or 16-bit mode, selected TCs can be cascaded to form a 32-bitTC, and the three Timer/Counters for Control have extended functions optimized for motor,lighting and other control applications. The series provide one full-speed USB 2.0 embedded hostand device interface; up to five Serial Communication Modules (SERCOM) that each can be configured to act as an USART, UART, SPI, I2C up 3.4MHz and LIN slave; up to eight channel350ksps 12-bit ADC with programmable gain and optional oversampling and decimationsupporting up to 16-bit resolution, two analog comparators with window mode, Peripheral TouchController supporting up to 48 buttons, sliders, wheels and proximity sensing; programmableWatchdog Timer, brown-out detector and power-on reset and two-pin Serial Wire Debug (SWD)program and debug interface.

　　All devices have accurate and low-power external and internal oscillators. All oscillators can beused as a source for the system clock. Different clock domains can be independently configuredto run at different frequencies, enabling power saving by running each peripheral at its optimalclock frequency, and thus maintaining a high CPU frequency while reducing power consumption.

　　The SAM R21 devices have two software-selectable sleep modes, idle and standby. In idle modethe CPU is stopped while all other functions can be kept running. In standby all clocks andfunctions are stopped expect those selected to continue running. The device supportsSleepWalking, which is the module’s ability to wake itself up and wake up its own clock, andhence perform predefined tasks without waking up the CPU. The CPU can then be only woken ona need basis, e.g. a threshold is crossed or a result is ready. The Event System supportssynchronous and asynchronous events, allowing peripherals to receive, react to and send eventseven in standby mode.

　　The Flash program memory can be reprogrammed in-system through the SWD interface. Thesame interface can be used for non-intrusive on-chip debug of application code. A boot loaderrunning in the device can use any communication interface to download and upgrade theapplication program in the Flash memory.

　　The SAM R21 devices are supported with a full suite of program and system development tools,including C compilers, macro assemblers, program debugger/simulators, programmers andevaluation kits.

　　SAM R21主要特性:

　　Processor
　　ARM Cortex-M0+ CPU running at up to 48MHz
　　Single-cycle hardware multiplier
　　Micro Trace Buffer (MTB)
　　Memories
　　768(1)/256/128/64KB in-system self-programmable Flash
　　32/16/8KB SRAM
　　System
　　Power-on reset (POR) and brown-out detection (BOD)
　　Internal and external clock options with 48MHz Digital Frequency Locked Loop (DFLL48M) and 48MHz to 96MHz FractionalDigital Phase Locked Loop(FDPLL96M)
　　External Interrupt Controller (EIC)
　　Up to 15 external interrupts
　　One non-maskable interrupt
　　Two-pin Serial Wire Debug (SWD) programming, test and debugging interface
　　Low Power
　　Idle and standby sleep modes
　　SleepWalking peripherals
　　Peripherals
　　12-channel Direct Memory Access Controller (DMAC)
　　12-channel Event System
　　Integrated Ultra Low Power Transceiver for 2.4GHz ISM Band
　　Supported PSDU Data rates: 250kb/s, 500kb/s, 1000kb/s and 2000kb/s
　　-99dBm RX Sensitivity; TX Output Power up to +4dBm
　　Hardware Assisted MAC (Auto-Acknowledge, Auto-Retry)
　　SFD-Detection; Spreading; De-Spreading; Framing; CRC-16 Computation
　　Antenna Diversity and TX/RX Control
　　128 Byte TX/RX Frame Buffer
　　Integrated 16MHz Crystal Oscillator (external crystal needed)
　　PLL synthesizer with 5 MHz and 500 kHz channel spacing for 2.4GHz ISM band
　　Hardware Security (AES, True Random Generator)
　　Three 16-bit Timer/Counters (TC), configurable as either:
　　One 16-bit TC with compare/capture channels
　　One 8-bit TC with compare/capture channels
　　One 32-bit TC with compare/capture channels, by using two TCs
　　Three 16-bit Timer/Counters for Control (TCC), with extended functions:
　　Up to four compare channels with optional complementary output
　　Generation of synchronized pulse width modulation (PWM) pattern across port pins
　　Deterministic fault protection, fast decay and configurable dead-time between complementary output
　　Dithering that increase resolution with up to 5 bit and reduce quantization error
　　32-bit Real Time Counter (RTC) with clock/calendar function
　　Watchdog Timer (WDT)
　　CRC-32 generator
　　One full-speed (12Mbps) Universal Serial Bus (USB) 2.0 interface
　　Embedded host and device function
　　Eight endpoints
　　Up to five Serial Communication Interfaces (SERCOM), each configurable to operate as either:
　　USART with full-duplex and single-wire half-duplex configuration
　　I2C up to 3.4MHz
　　SPI
　　LIN slave
　　One 12-bit, 350ksps Analog-to-Digital Converter (ADC) with up to eight external channels
　　Differential and single-ended input
　　1/2x to 16x programmable gain stage
　　Automatic offset and gain error compensation
　　Oversampling and decimation in hardware to support 13-, 14-, 15- or 16-bit resolution
　　Two Analog Comparators (AC) with window compare function
　　Peripheral Touch Controller (PTC)
　　48-channel capacitive touch and proximity sensing
　　I/O and Package
　　16/28 programmable I/O pins
　　32-pin and 48-pin QFN
　　Operating Voltage
　　1.8V – 3.6V
　　Temperature Range
　　-40℃ to 85℃ Industrial
　　-40℃ to 125℃ Industrial

　　图1.SAM R21 MCU框图

　　图2.SAM R21内部连接图

　　具有ZigBee光连接的ATSAMR21 LED驱动器AT13518

　　Atmel® ATSAMR21-LED-Driver is a reference platform that uses Atmel SAMR21 an IEEE 802.15.4 compliant SoC which incorporates an ARM® Cortex®M0+ based 32-bit microcontroller and a 2.4GHz RF transceiver to wirelesslycontrol LEDs in a constant current DC-DC step-down topology.

　　Atmel ATSAMR21-LED-DRIVER Development Kit demonstrates a wirelessdimmable LED driver module based on DC-DC buck converter providingconstant current to the LEDs, operating in boundary conduction modeimplemented in firmware of Atmel SAM R21 without using any external DCDCLED driver IC.

　　LED reference board is powered by a 24V AC-DC universal adaptor andcapable of driving 14V onboard LED load with 6W power and is scalable tohigher watts and other LED configurations. This document guides user torecalculate driver parameters and values of passive components on LEDdriver board.

　　ATSAMR21 LED驱动器主要特性:

　　• Industry’s first IEEE® 802.15.4 standard compliant 2.4GHz wirelessMCU with LED driving capability

　　• Complete LED driver evaluation platform using Atmel SAM R21

　　• Supports ZigBee® Light Link (ZLL) stack

　　• Compatible with ZigBee Home Automation (ZHA) protocols

　　• 0.5% to 100% dimming using combination of analog and PWM dimming

　　• Up to 96% efficiency

　　• Preconfigured to generate 6W output for four LEDs

　　• AVR477 wireless touch remote controller for dimming and other LEDControls

　　ATSAMR21 LED驱动器评估板包括:

　　• 1 - SAM R21 Xplained Pro (ATSAMR21-XPRO) board with modified connectors

　　• 1 - LED driver board

　　• 1 - LED load board with diffuser

　　• 1 - 24V AC-DC universal adaptor

　　• 1 - Atmel AVR477 wireless touch remote controller

　　图3.ATSAMR21 LED驱动器评估板外形图

　　图4.ATSAMR21 LED驱动器评估板框图

　　图5.ATSAMR21 LED驱动器评估板电路图:LED驱动器

　　图6.ATSAMR21 LED驱动器评估板电路图:LDO稳压器和过压保护

　　图7.ATSAMR21 LED驱动器评估板电路图:LED驱动器插头

　　图8.ATSAMR21 LED驱动器评估板LED负载电路图

　　ATSAMR21 LED驱动器评估板材料清单(BOM):

　　图9.ATSAMR21 LED驱动器评估板装配图:顶层

　　图10.ATSAMR21 LED驱动器评估板LED驱动器板装配图:底层

　　图11.ATSAMR21 LED驱动器评估板LED负载板装配图:顶层