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local scd4x = {}
local device_address = 0x62
scd4x.bus_id = 0
function scd4x.start()
i2c.start(scd4x.bus_id)
if not i2c.address(scd4x.bus_id, device_address, i2c.TRANSMITTER) then
return false
end
i2c.write(scd4x.bus_id, {0x21, 0xb1})
i2c.stop(scd4x.bus_id)
return true
end
function scd4x.stop()
i2c.start(scd4x.bus_id)
if not i2c.address(scd4x.bus_id, device_address, i2c.TRANSMITTER) then
return false
end
i2c.write(scd4x.bus_id, {0x3f, 0x86})
i2c.stop(scd4x.bus_id)
return true
end
function scd4x.read()
i2c.start(scd4x.bus_id)
if not i2c.address(scd4x.bus_id, device_address, i2c.TRANSMITTER) then
return nil
end
i2c.write(scd4x.bus_id, {0xec, 0x05})
i2c.stop(scd4x.bus_id)
i2c.start(scd4x.bus_id)
if not i2c.address(scd4x.bus_id, device_address, i2c.RECEIVER) then
return nil
end
local data = i2c.read(scd4x.bus_id, 9)
i2c.stop(scd4x.bus_id)
local co2 = string.byte(data, 1) * 256 + string.byte(data, 2)
local temp_raw = 175 * (string.byte(data, 4) * 256 + string.byte(data, 5))
local humi_raw = 100 * (string.byte(data, 7) * 256 + string.byte(data, 8))
return co2, temp_raw, humi_raw
end
return scd4x
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