AVR ATMEGA2A-PU低输出电压

Question

我刚刚开始尝试直接使用AVR，而不是使用像Arduino Uno这样的开发板。我看到的问题是，当我试图在输出引脚上驱动一堆LED时，其中许多LED读取的电压非常低，远低于预期的5V。

我正在用14MHz的晶体运行代码。我已将AVR上的保险丝设置为：lfuse：0xFFhfuse:0x89晶体连接到引脚XTAL1&XTAL2.晶体的每根引线也通过22pF陶瓷电容器连接到GND。

我在VCC和GND之间连接了一个.1uF电解帽，在AVCC和GND上连接了另一个，阴极（-）连接到GND端子。在我的电源端子上还有一个10uF的电解帽。

ATMEGA20A的连接如下：PB0-7:打开RESET:10K电阻器到VCCVCC:5VGND:GNDXTAL1：水晶XTAL2：水晶PD0-7:510欧姆电阻器至LED至GNDPC0-7:510欧姆电阻器至LED至GNDAVCC:5VGND:GNDAREF:5V（也尝试过这种打开。没有变化）PA0-7：打开

PORTD似乎工作得很好。我得到了从AVR到每个引脚接地的4.6V压降。然而，PORTC工作不正常。当我从C0向上移动时，每个引脚的电压降随着我向上移动PORTC而减小。PC0给出的电压几乎是4.6V。当我到达C7时，电压逐渐降低，测量值为2.2V。

发生这种情况有什么特别的原因吗？我是否缺少AVR所需的某种类型的连接？下面是我非常简单的代码和makefile。

主

#include <avr/io.h>
void setup();
void setup()
{
  DDRD=0XFF;
  PORTD = 0xff;
  DDRC |= 0XfF;
  PORTC = 0xff;
}
int main()
{
  setup();
  while(1)
  {
  }
  return 0;
}

生成文件

MCU = atmega32
# Target file name (without extension).
TARGET = main
AVRDUDE_PROGRAMMER = avrisp
AVRDUDE_PORT = COM3
OPT = s
FORMAT = ihex
SRC = $(TARGET).c
#SRC += TimerOne.cpp
EXTRAINCDIRS = 
CLOCK = 14745600
CPU = F_CPU=$(CLOCK)

# Optional compiler flags.
#  -g:        generate debugging information (for GDB, or for COFF conversion)
#  -O*:       optimization level
#  -f...:     tuning, see gcc manual and avr-libc documentation
#  -Wall...:  warning level
#  -Wa,...:   tell GCC to pass this to the assembler.
#    -ahlms:  create assembler listing
CFLAGS = -g -O$(OPT) 
-funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -Wall 
$(patsubst %,-I%,$(EXTRAINCDIRS))
# -lm = math library
LDFLAGS = -lm
AVRDUDE = avrdude
AVRDUDE_WRITE_FLASH = -U flash:w:$(TARGET).hex
AVRDUDE_FLAGS = -p $(MCU) -P $(AVRDUDE_PORT) -c $(AVRDUDE_PROGRAMMER) -b 19200
AVRDUDE_FLAGS += -v
# ---------------------------------------------------------------------------
# Define directories, if needed.
DIRAVR = c:/winavr
DIRAVRBIN = $(DIRAVR)/bin
DIRAVRUTILS = $(DIRAVR)/utils/bin
DIRINC = .
DIRLIB = $(DIRAVR)/avr/lib
# Define programs and commands.
CC = avr-g++ -D$(CPU) -D$(MCU)
OBJCOPY = avr-objcopy
OBJDUMP = avr-objdump
SIZE = avr-size
REMOVE = rm -f
COPY = cp
HEXSIZE = $(SIZE) --target=$(FORMAT) $(TARGET).hex
ELFSIZE = $(SIZE) -AC --mcu=$(MCU) $(TARGET).elf
# Define all object files.
OBJ = $(patsubst src%,obj$(VERSION)%,$(patsubst %.c,%.o,$(SRC)))
# Define all listing files.
LST = $(ASRC:.S=.lst) $(SRC:.c=.lst)
# Combine all necessary flags and optional flags.
# Add target processor to flags.
ALL_CFLAGS = -mmcu=$(MCU) -I. $(CFLAGS)
ALL_ASFLAGS = -mmcu=$(MCU) -I. -x assembler-with-cpp $(ASFLAGS)
# Default target: make program!
all: main.hex
main.hex: main.elf
    $(OBJCOPY) -O $(FORMAT) -R .eeprom main.elf main.hex
main.elf:  main.o
    $(CC) $(ALL_CFLAGS) main.o --output main.elf $(LDFLAGS)
main.o: 
    @echo
    @echo $(MSG_COMPILING) $<
    $(CC) -c $(ALL_CFLAGS) main.c -o $@
# Program the device.  
program: $(TARGET).hex
    $(AVRDUDE) $(AVRDUDE_FLAGS) -U flash:w:$(TARGET).hex
# Flash the device
flash:
    $(AVRDUDE) $(AVRDUDE_FLAGS) -U lfuse:w:0xFF:m -U hfuse:w:0x89:m
# Target: clean project.
clean: begin clean_list finished end
clean_list :
    @echo
    @echo $(MSG_CLEANING)
    $(REMOVE) $(TARGET).hex
    $(REMOVE) $(TARGET).eep
    $(REMOVE) $(TARGET).obj
    $(REMOVE) $(TARGET).cof
    $(REMOVE) $(TARGET).elf
    $(REMOVE) $(TARGET).map
    $(REMOVE) $(TARGET).obj
    $(REMOVE) $(TARGET).a90
    $(REMOVE) $(TARGET).sym
    $(REMOVE) $(TARGET).lnk
    $(REMOVE) $(TARGET).lss
    $(REMOVE) $(TARGET).o
# Listing of phony targets.
.PHONY : all begin finish end sizebefore sizeafter gccversion coff extcoff 
    clean clean_list program

Answer 1

经过几天的搜索，我似乎只需要问这个问题，就可以自己找到答案。通常情况下，答案在数据表中。问题出在保险丝片上。默认情况下，JTAG接口已启用，它是PORTC的一部分。这就是PORTC工作不正常的原因。我将HFUSE位从0x89更新为0xC9。这禁用了JTAG接口，PORTC的行为与普通IO端口类似。