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local sen5x = {}
local device_address = 0x69
sen5x.bus_id = 0
function sen5x.start()
i2c.start(sen5x.bus_id)
if not i2c.address(sen5x.bus_id, device_address, i2c.TRANSMITTER) then
return false
end
i2c.write(sen5x.bus_id, {0x00, 0x21})
i2c.stop(sen5x.bus_id)
return true
end
function sen5x.stop()
i2c.start(sen5x.bus_id)
if not i2c.address(sen5x.bus_id, device_address, i2c.TRANSMITTER) then
return false
end
i2c.write(sen5x.bus_id, {0x01, 0x04})
i2c.stop(sen5x.bus_id)
return true
end
function sen5x.read_value(data, index)
local val = string.byte(data, index) * 256 + string.byte(data, index+1)
if val == 0xffff or val == 0x7fff then
val = nil
end
return val
end
function sen5x.prepare_read()
i2c.start(sen5x.bus_id)
if not i2c.address(sen5x.bus_id, device_address, i2c.TRANSMITTER) then
return false
end
i2c.write(sen5x.bus_id, {0x03, 0xc4})
i2c.stop(sen5x.bus_id)
return true
end
function sen5x.read()
i2c.start(sen5x.bus_id)
if not i2c.address(sen5x.bus_id, device_address, i2c.RECEIVER) then
return false
end
local data = i2c.read(sen5x.bus_id, 24)
i2c.stop(sen5x.bus_id)
if not sen5x.crc_valid(data, 24) then
return false
end
sen5x.pm1 = sen5x.read_value(data, 1)
sen5x.pm2_5 = sen5x.read_value(data, 4)
sen5x.pm4 = sen5x.read_value(data, 7)
sen5x.pm10 = sen5x.read_value(data, 10)
sen5x.humidity = sen5x.read_value(data, 13)
sen5x.temperature = sen5x.read_value(data, 16)
sen5x.voc = sen5x.read_value(data, 19)
sen5x.nox = sen5x.read_value(data, 22)
return true
end
function sen5x.prepare_get_product()
i2c.start(sen5x.bus_id)
if not i2c.address(sen5x.bus_id, device_address, i2c.TRANSMITTER) then
return false
end
i2c.write(sen5x.bus_id, {0xd0, 0x14})
i2c.stop(sen5x.bus_id)
return true
end
function sen5x.get_product()
i2c.start(sen5x.bus_id)
if not i2c.address(sen5x.bus_id, device_address, i2c.RECEIVER) then
return nil
end
local data = i2c.read(sen5x.bus_id, 48)
i2c.stop(sen5x.bus_id)
if not sen5x.crc_valid(data, 48) then
return false
end
local ret = ""
ret = ret .. string.sub(data, 1, 2)
ret = ret .. string.sub(data, 4, 5)
ret = ret .. string.sub(data, 7, 7)
return ret
end
function sen5x.crc_word(data, index)
local crc = 0xff
for i = index, index+1 do
crc = bit.bxor(crc, string.byte(data, i))
for j = 8, 1, -1 do
if bit.isset(crc, 7) then
crc = bit.bxor(bit.lshift(crc, 1), 0x31)
else
crc = bit.lshift(crc, 1)
end
crc = bit.band(crc, 0xff)
end
end
return bit.band(crc, 0xff)
end
function sen5x.crc_valid(data, length)
for i = 1, length, 3 do
if sen5x.crc_word(data, i) ~= string.byte(data, i+2) then
return false
end
end
return true
end
return sen5x
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