66 lines
1.6 KiB
Lua
66 lines
1.6 KiB
Lua
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------------------------------------------------------------------------------
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-- DS18B20 query module
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--
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-- LICENCE: http://opensource.org/licenses/MIT
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-- Vladimir Dronnikov <dronnikov@gmail.com>
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--
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-- Example:
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-- for k, v in pairs(require("ds18b20").read(4)) do print(k, v) end
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------------------------------------------------------------------------------
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local M
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do
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local format_addr = function(a)
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return ("%02x-%02x%02x%02x%02x%02x%02x"):format(
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a:byte(1),
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a:byte(7), a:byte(6), a:byte(5),
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a:byte(4), a:byte(3), a:byte(2)
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)
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end
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local read = function(pin, delay)
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local ow = require("ow")
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-- get list of relevant devices
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local d = { }
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ow.setup(pin)
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ow.reset_search(pin)
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while true do
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tmr.wdclr()
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local a = ow.search(pin)
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if not a then break end
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if ow.crc8(a) == 0 and
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(a:byte(1) == 0x10 or a:byte(1) == 0x28)
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then
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d[#d + 1] = a
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end
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end
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-- conversion command for all
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ow.reset(pin)
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ow.skip(pin)
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ow.write(pin, 0x44, 1)
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-- wait a bit
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tmr.delay(delay or 100000)
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-- iterate over devices
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local r = { }
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for i = 1, #d do
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tmr.wdclr()
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-- read rom command
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ow.reset(pin)
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ow.select(pin, d[i])
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ow.write(pin, 0xBE, 1)
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-- read data
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local x = ow.read_bytes(pin, 9)
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if ow.crc8(x) == 0 then
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local t = (x:byte(1) + x:byte(2) * 256) * 625
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-- NB: temperature in Celcius * 10^4
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r[format_addr(d[i])] = t
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d[i] = nil
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end
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end
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return r
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end
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-- expose
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M = {
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read = read,
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}
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end
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return M
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