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Page 181

import subprocess
import io
import fcntl


def checkI2CBus():
    temp = subprocess.Popen(["sudo", "dtparam", "-l"], stdout=subprocess.PIPE)
    output = str(temp.communicate())
    lasti2c = output.rfind("i2c_arm")
    if lasti2c != -1:
        lasti2c = output.find("i2c_arm=on", lasti2c)
    if lasti2c == -1:
        temp = subprocess.Popen(["sudo", "dtparam", "i2c_arm=on"],  stdout=subprocess.PIPE)
        output = str(temp.communicate())
    return


checkI2CBus()

I2C_SLAVE = 0x0703

fdr = io.open("/dev/i2c-1", "rb", buffering=0)
fdw = io.open("/dev/i2c-1", "wb", buffering=0)
fcntl.ioctl(fdr, I2C_SLAVE, 0x40)
fcntl.ioctl(fdw, I2C_SLAVE, 0x40)
fdw.write(bytearray([0xE7]))
data = fdr.read(1)
print(data)
fdr.close()
fdw.close()

Page 183

import subprocess
import io
import fcntl
from time import sleep

checkI2CBus()
I2C_SLAVE = 0x0703

fdr = io.open("/dev/i2c-1", "rb", buffering=0)
fdw = io.open("/dev/i2c-1", "wb", buffering=0)
fcntl.ioctl(fdr, I2C_SLAVE, 0x40)
fcntl.ioctl(fdw, I2C_SLAVE, 0x40)

fdw.write(bytearray([0xF3]))
while(True):
    try:
        data = fdr.read(3)
        break
    except:
        sleep(0.01)
msb = data[0]
lsb = data[1]
crc = data[2]
print("msb=", msb, " lsb=", lsb, " crc=", crc)

fdw.close()
fdr.close()

Page 187

import subprocess
import io
import fcntl
from time import sleep


def crcCheck(msb, lsb, check):
    data32 = (msb << 16) | (lsb << 8) | check
    divisor = 0x988000
    for i in range(16):
        if(data32 & 1 << (23 - i)):
            data32 ^= divisor
        divisor >>= 1
    return data32


def checkI2CBus():
    temp = subprocess.Popen(["sudo", "dtparam", "-l"],  stdout=subprocess.PIPE)
    output = str(temp.communicate())
    print(output)
    lasti2c = output.rfind("i2c_arm")
    if lasti2c != -1:
        lasti2c = output.find("i2c_arm=on", lasti2c)
    if lasti2c == -1:
        temp = subprocess.Popen(["sudo", "dtparam", "i2c_arm=on"],  stdout=subprocess.PIPE)
        output = str(temp.communicate())
    return


checkI2CBus()
I2C_SLAVE = 0x0703

fdr = io.open("/dev/i2c-1", "rb", buffering=0)
fdw = io.open("/dev/i2c-1", "wb", buffering=0)
fcntl.ioctl(fdr, I2C_SLAVE, 0x40)
fcntl.ioctl(fdw, I2C_SLAVE, 0x40)

fdw.write(bytearray([0xF3]))
while(True):
    try:
        data = fdr.read(3)
        break
    except:
        sleep(0.01)
msb = data[0]
lsb = data[1]
crc = data[2]

data16 = (msb << 8) | (lsb & 0xFC)
temp = -46.85 + (175.72 * data16 / 65536)
print("Temperature=", temp, "C")

fdw.write(bytearray([0xF5]))
while(True):
    try:
        data = fdr.read(3)
        break
    except:
        sleep(0.01)

msb = data[0]
lsb = data[1]
crc = data[2]
data16 = (msb << 8) | (lsb & 0xFC)
hum = -6 + 125.0 * data16 / 65536

print("humidity=", hum, "%")

print(crcCheck(msb, lsb, crc))
fdw.close()
fdr.close()