-
MSP430F149
的
ADC12
模块
1
概述
M
SP430F149
的
ADC12
为<
/p>
SAR
型
12
位
AD,
共有
16
路输入通道,其中
8
路独立的外部输入通道,
2
路接
外部
Vref+,Vr
ef-
,
3
路内部通道可分别测内部温
度传感器、
AVCC
、和外部参考源。
P6
口第二功能为
AD
输入端。
MSP430F149
的
10
、
11
分别接外部电压参考源正负极,
7
脚可将内部电压<
/p>
参考源输出。
ADC12
共有
18
个中断源
,公用一个中断向量
ADC12_VECTOR
。
AD
的参考源可选择内部电压参考源或外部电压参
考源。内部电压参考源有
1.5V,2.5V
可选,使用时向<
/p>
ADC12CTL0
写入
REFON+
REF2_5V
就打开了
2.5V
。<
/p>
外部电压参考源由
REF+
接入。
上电时若不设置参考源,
则参考源为系统供电电压
3.3V
。
2
使用方法概述
2.1
程序架构
中断方式
1
、设置
ADC12
工作模式,启动转换,开全局中断,等待中断
2
、写中断处理函数
查询方式
< br>设置
ADC12
工作模式,启动转换,查询中断标志
p>
ADC12IFG
while
(!(0x01 & ADC12IFG));
转换完毕读取采样值,系统自动清除中断
标志
2.2
使用概述
主要参数配置
设置工作方式:
singsequencere-
singre-sequencd;
设置转换时间:
SHTX
设置触发方式:
ADC12SCMSCTimerA
TimerB
设置通道:外部通道
内部
Temperature sensor
设置参考源:系统电压
内部参考源
外部参考源
其他细节配置
一般要配置采样转换模式为脉冲
(<
/p>
SHP
)
,
打开
ADC12(ADC12ON),
使能
ADC12
转换
(ENC)
,
使能中断
(如
果采取中断模式),触发转换(若
采用
ADC12SC
触发)。
解释
ADC12
< br>模数转换是在
SHI
的上升沿初始化的。
SHI
信号有四个来源:
The ADC12SC
bit
;
The Timer_A
Output Unit 1
;
The Timer_B Output Unit
0
;
The Timer_B
Output Unit 1
。故单次采样时只需要每次
设置<
/p>
ADC12CTL0 |=
ADC12SC
就采样一次;重复采样时,如
Rep-
sing
,设置
ADC12CTL1 = SHS_1
+CONSEQ_2
就选择了
Rep-
sing
模式,每次采样通过定时器
A
触发。
3
相关寄存器
1
、
ADC12CTL0
SHT1x Bits
Sample-and-hold
time. These bits define the number of ADC12CLK
cycles in
the sampling period for
registers ADC12MEM8 to ADC12MEM15.
SHT0x Bits
Sample-and-hold
time. These bits define the number of ADC12CLK
cycles in
the sampling period for
registers ADC12MEM0 to ADC12MEM7.
ADC12ON
0 ADC12 off
1 ADC12 on
ENC
ENC Bit 1 Enable conversion
0 ADC12 disabled
1 ADC12
enabled
ADC12SC Bit 0 Start conversion.
Software-controlled sample-and-conversion start.
ADC12SC and ENC may be set together
with one instruction. ADC12SC is
reset
automatically.
0 No sample-and-
conversion-start
1 Start sample-and-
conversion
MSC Bit 7 Multiple sample
and conversion. Valid only for sequence or
repeated modes.
0 The sampling timer
requires a rising edge of the SHI signal to
trigger
each sample-and-conversion.
1 The first rising edge of the SHI
signal triggers the sampling timer, but
further sample-and-conversions are
performed automatically as soon
as the
prior conversion is completed.
2
、
ADC12CTL1
SHP
SHP Bit 9 Sample-and-
hold pulse-mode select. This bit selects the
source of the
sampling signal (SAMPCON)
to be either the output of the sampling timer or
the sample-input signal directly.
0 SAMPCON signal is sourced from the
sample-input signal.
1 SAMPCON signal
is sourced from the sampling timer.
SHSx Bits
11-10
Sample-and-hold source select
00 ADC12SC bit
01 Timer_1
10 Timer_0
11 Timer_1
CONSEQx Bits
2-1
Conversion sequence mode select
00 Single-channel, single-conversion
01 Sequence-of-channels
10
Repeat-single-channel
11 Repeat-
sequence-of-channels
3
、
ADC12IE
ADC12IEx Bits
15-0
Interrupt enable. These bits enable or
disable the interrupt request for the ADC12IFGx
bits.
0 Interrupt disabled
1
Interrupt enabled
4
、
ADC12IFG
ADC12IFGx Bits
15-0
ADC12MEMx Interrupt flag. These bits
are set when corresponding
ADC12MEMx is
loaded with a conversion result. The ADC12IFGx
bits are
reset if the corresponding
ADC12MEMx is accessed, or may be reset with
software.
0 No interrupt
pending
1 Interrupt pending
5
、
ADC12MCTLX
SREFx Bits
6-4
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