AVR微控制器编程初学者教程

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"AVR编程初学者指南，涵盖了如何与微控制器进行交互的教程，包括AVR 8位微控制器的高性能、低功耗特性，高级RISC架构，以及丰富的外设功能，如定时器、PWM通道和串行接口等。" 在开始AVR编程的旅程时，了解基础至关重要。AVR是一种高级精简指令集计算（RISC）架构的8位微控制器，由Atmel（现被Microchip Technology收购）开发。它的主要特点在于高效能和低功耗，这使得AVR微控制器在嵌入式系统、物联网设备和电子项目中广泛应用。 AVR的RISC架构设计使其具备以下特性： 1. **强大指令集**：AVR微控制器拥有130条强大的指令，并且大多数指令可以在单个时钟周期内执行，这极大地提高了代码执行速度。 2. **通用寄存器**：32个8位的通用目的工作寄存器提供快速数据处理能力。 3. **静态操作**：能够在各种工作模式下保持稳定运行，无需动态切换。 4. **高吞吐量**：在16MHz的时钟频率下，可达到每秒16百万条指令（MIPS）的处理速度。 5. **片上乘法器**：内置的2周期乘法器可进一步加速数学运算。在内存方面，AVR微控制器提供以下非易失性存储器（NVM）段： 1. **闪存程序存储器**：8KB的在系统自编程闪存，用于存储程序代码，支持10,000次写/擦除循环。 2. **EEPROM**：512字节的电可擦可编程只读存储器（EEPROM），支持100,000次写/擦除周期，用于数据存储。 3. **内部静态RAM（SRAM）**：1KB的SRAM用于临时数据存储，速度快，但断电后数据会丢失。在系统编程（ISP）功能允许通过片上的Bootloader在系统内更新程序，无需额外的编程设备。此外，还有独立的锁定位以保护软件安全。 AVR微控制器的外设功能包括： 1. **定时器/计数器**：两个8位定时器/计数器和一个16位定时器/计数器，带有单独的预分频器和比较模式。 2. **实时时钟（RTC）**：带有独立振荡器的实时时钟模块，用于时间管理。 3. **脉宽调制（PWM）通道**：三个PWM通道，广泛用于电机控制和模拟信号生成。 4. **模数转换器（ADC）**：8通道10位精度的ADC，对于PDIP封装的设备为6通道，适用于各种传感器输入。 5. **两线串行接口**：字节导向的两线串行接口，如I²C，可用于与其他设备通信。 AVR编程初学者需要掌握这些基础知识，包括硬件选择、电路设计、编程语言（通常使用C或汇编）、使用IDE（如Atmel Studio）以及调试技巧。随着对AVR架构和编程的深入理解，你可以构建出复杂而高效的嵌入式系统。通过不断实践和学习，你可以逐步成长为一名熟练的AVR开发者。

2486T–AVR–05/08

ATmega8(L)

When using the SEI instruction to enable interrupts, the instruction following SEI will be exe-

cuted before any pending interrupts, as shown in the following example.

Interrupt Response

Time

The interrupt execution response for all the enabled AVR interrupts is four clock cycles mini-

mum. After four clock cycles, the Program Vector address for the actual interrupt handling

routine is executed. During this 4-clock cycle period, the Program Counter is pushed onto the

Stack. The Vector is normally a jump to the interrupt routine, and this jump takes three clock

cycles. If an interrupt occurs during execution of a multi-cycle instruction, this instruction is com-

pleted before the interrupt is served. If an interrupt occurs when the MCU is in sleep mode, the

interrupt execution response time is increased by four clock cycles. This increase comes in addi-

tion to the start-up time from the selected sleep mode.

A return from an interrupt handling routine takes four clock cycles. During these four clock

cycles, the Program Counter (2 bytes) is popped back from the Stack, the Stack Pointer is incre-

mented by 2, and the I-bit in SREG is set.

Assembly Code Example

sei ; set global interrupt enable

sleep; enter sleep, waiting for interrupt

; note: will enter sleep before any pending

; interrupt(s)

C Code Example

_SEI(); /* set global interrupt enable */

_SLEEP(); /* enter sleep, waiting for interrupt */

/* note: will enter sleep before any pending interrupt(s) */

2486T–AVR–05/08

ATmega8(L)

The EEPROM Address

EEARL

• Bits 15..9 – Res: Reserved Bits

These bits are reserved bits in the ATmega8 and will always read as zero.

• Bits 8..0 – EEAR8..0: EEPROM Address

The EEPROM Address Registers – EEARH and EEARL – specify the EEPROM address in the

512 bytes EEPROM space. The EEPROM data bytes are addressed linearly between 0 and

511. The initial value of EEAR is undefined. A proper value must be written before the EEPROM

may be accessed.

The EEPROM Data

• Bits 7..0 – EEDR7..0: EEPROM Data

For the EEPROM write operation, the EEDR Register contains the data to be written to the

EEPROM in the address given by the EEAR Register. For the EEPROM read operation, the

EEDR contains the data read out from the EEPROM at the address given by EEAR.

The EEPROM Control

• Bits 7..4 – Res: Reserved Bits

These bits are reserved bits in the ATmega8 and will always read as zero.

• Bit 3 – EERIE: EEPROM Ready Interrupt Enable

Writing EERIE to one enables the EEPROM Ready Interrupt if the I bit in SREG is set. Writing

EERIE to zero disables the interrupt. The EEPROM Ready interrupt generates a constant inter-

rupt when EEWE is cleared.

• Bit 2 – EEMWE: EEPROM Master Write Enable

The EEMWE bit determines whether setting EEWE to one causes the EEPROM to be written.

When EEMWE is set, setting EEWE within four clock cycles will write data to the EEPROM at

the selected address If EEMWE is zero, setting EEWE will have no effect. When EEMWE has

been written to one by software, hardware clears the bit to zero after four clock cycles. See the

description of the EEWE bit for an EEPROM write procedure.

• Bit 1 – EEWE: EEPROM Write Enable

The EEPROM Write Enable Signal EEWE is the write strobe to the EEPROM. When address

and data are correctly set up, the EEWE bit must be written to one to write the value into the

EEPROM. The EEMWE bit must be written to one before a logical one is written to EEWE, oth-

Bit 151413121110 9 8

–––––––EEAR8EEARH

EEAR7 EEAR6 EEAR5 EEAR4 EEAR3 EEAR2 EEAR1 EEAR0 EEARL

76543210

Read/WriteRRRRRRRR/W

R/W R/W R/W R/W R/W R/W R/W R/W

Initial Value0000000X

XXXXXXXX

Bit 76543210

MSB LSB EEDR

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

Initial Value00000000

Bit 76543210

– – – – EERIE EEMWE EEWE EERE EECR

Read/Write R R R R R/W R/W R/W R/W

Initial Value 0 0 0 0 0 0 X 0

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AVR微控制器编程初学者教程

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r = sqrt(xx_avr-2*x00*x_avr+x00*x00 + yy_avr-2*y00*y_avr+y00*y00 + zz_avr-2*z00*z_avr+z00*z00); %拟合出的球半径r

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r = sqrt(xx_avr-2x00x_avr+x00x00 + yy_avr-2y00y_avr+y00y00 + zz_avr-2z00z_avr+z00*z00); %拟合出的球半径r