几年前买的树莓派几乎没动，相对于Beaglebone太弱了，不过Rpi社区比Beaglebone活跃很多。
PM2.5传感器
女朋友喉咙不太舒服，所以买了一个Pm2.5的Sensor监测一下空气质量，经过UART封装后可以轻松的连接到MCU，一个大洋150左右。注意不要买粉尘传感器，粉尘传感器分辨率太低。
构建Rpi的运行系统
素不喜欢定制的Debian之类系统，必须Buildroot一路自行编译uboot、kernel和rootfs下载到SD卡。
添加USB无线适配器驱动
我使用RTL8192芯片的EDUP NP8508GS适配器，需要编译RTL8192系列驱动，并在系统启动时modprobe。
设置wp_suplication
主要在
/etc/wpa_supplicant.conf文件中设置无限ssid和密码，网关和dns看需要设置。Python读取PM2.5传感器数值
读出的数据已经被转成数字信号了，可以直接拿来换算。代码如下：
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#! /usr/bin/env python
# -*- coding: utf-8 -*-
#
# email sent app
# by leon@2015-07-09
#
# curl -d "{\"value\":50}" -H "U-ApiKey: my_key" 'my_url'
#
import time
import json
import requests
# example: http://api.yeelink.net/v1.1/device/115088/sensor/144111/datapoints
class YeelinkHelper:
url = 'http://api.yeelink.net/v1.1'
key = ''
hdr = ''
dev = ''
sensors = []
def __init__(self,key,dev,sensors):
self.key = key
self.dev = dev
self.sensors = sensors
self.hdr = {'U-ApiKey':key,'content-type': 'application/json'}
def up(self,vals):
idx = 0
utime=time.strftime("%Y-%m-%dT%H:%M:%S")
for sen in self.sensors:
if idx < len(vals):
post_url=r'%s/device/%s/sensor/%s/datapoints' % (self.url, self.dev, sen)
data={"timestamp":utime , "value": vals[idx]}
res=requests.post(post_url,headers=self.hdr,data=json.dumps(data))
idx += 1
print("utime:%s, url:%s, status_code:%d" %(utime,post_url,res.status_code))
print(self.hdr)
print(json.dumps(data))
6.注册Yeelink账号并编写python数据上传脚本 yeelink的IOT（物联网）服务可添加简单的传感器数值，由平台保存数据并进行可视化。其上传格式可参见开发者API手册。上传部分代码如下：
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#! /usr/bin/env python
# -*- coding: utf-8 -*-
#
# pms module detect
# by leon@2015-07-09
#
#
# -*- coding: utf-8 -*-
import serial
from yeelink import YeelinkHelper
# global enum
DATALEN = 10
SBYTE = 0xaa
EBYTE = 0xab
HDR_IDX = 0 #0xaa
CMD_IDX = 1
PM25L_IDX = 2
PM25H_IDX = 3
PM10L_IDX = 4
PM10H_IDX = 5
R1_IDX = 6
R2_IDX = 7
CHK_IDX = 8
END_IDX = 9 #0xab
# yeelink
YEELINK_API_KAY = 'my_key'
YEELINK_DEV = '115167'
# pm2.5, pm10, cpu_temp
YEELINK_SENSORS = ['144020','144022','144483']
class RPiDev:
@staticmethod
def get_cpu_temp():
cpu_temp_file = open( "/sys/class/thermal/thermal_zone0/temp" )
cpu_temp = cpu_temp_file.read()
cpu_temp_file.close()
return float(cpu_temp)/1000
class PmsMod:
def __init__(self,p,ydev):
self.port = p
self.idx = 0
self.maxLen = DATALEN*2
self.datas = [0]*self.maxLen
self.ydev = ydev
def getPm25(self,pos):
offset = pos*DATALEN + PM25L_IDX
return float(self.datas[offset]+256*self.datas[offset+1])/10;
def getPm10(self,pos):
offset = pos*DATALEN + PM10L_IDX
return float(self.datas[offset]+256*self.datas[offset+1])/10;
def collect(self):
# read firs start byte
byte=ord(self.port.read())
while byte != EBYTE:
byte=ord(self.port.read())
print(byte)
self.idx = 0
count = 0
while True:
byte = self.port.read()
self.datas[self.idx] = ord(byte)
self.idx += 1
if self.idx == self.maxLen:
count+=1
# every 5*2=10s
if count >= 5:
pos = self.idx/DATALEN-1
pm25 = self.getPm25(pos)
pm10 = self.getPm10(pos)
cpu_temp = RPiDev.get_cpu_temp()
vals = [int(pm25),int(pm10),int(cpu_temp)]
self.ydev.up(vals)
print("pm25=%.1fug/m3, pm10=%.1fug/m3 tmp=%.1f'C" %(pm25,pm10,cpu_temp))
count = 0
self.idx = 0
if __name__ == "__main__":
ydev1 = YeelinkHelper(YEELINK_API_KAY,YEELINK_DEV,YEELINK_SENSORS)
port = serial.Serial("/dev/ttyAMA0",baudrate=9600,bytesize=8,parity='N',stopbits=1,xonxoff=0,timeout=3.0)
mod = PmsMod(port,ydev1)
mod.collect()
port.close()