74 lines
1.9 KiB
Lua
74 lines
1.9 KiB
Lua
------------------------------------------------------------------------------
|
|
-- DS18B20 query module
|
|
--
|
|
-- LICENCE: http://opensource.org/licenses/MIT
|
|
-- Vladimir Dronnikov <dronnikov@gmail.com>
|
|
--
|
|
-- Example:
|
|
-- require("ds18b20").read(4, function(r) for k, v in pairs(r) do print(k, v) end end)
|
|
------------------------------------------------------------------------------
|
|
local M
|
|
do
|
|
local bit = bit
|
|
local format_addr = function(a)
|
|
return ("%02x-%02x%02x%02x%02x%02x%02x"):format(
|
|
a:byte(1),
|
|
a:byte(7), a:byte(6), a:byte(5),
|
|
a:byte(4), a:byte(3), a:byte(2)
|
|
)
|
|
end
|
|
local read = function(pin, cb, delay)
|
|
local ow = require("ow")
|
|
-- get list of relevant devices
|
|
local d = { }
|
|
ow.setup(pin)
|
|
ow.reset_search(pin)
|
|
while true do
|
|
tmr.wdclr()
|
|
local a = ow.search(pin)
|
|
if not a then break end
|
|
if ow.crc8(a) == 0 and
|
|
(a:byte(1) == 0x10 or a:byte(1) == 0x28)
|
|
then
|
|
d[#d + 1] = a
|
|
end
|
|
end
|
|
-- conversion command for all
|
|
ow.reset(pin)
|
|
ow.skip(pin)
|
|
ow.write(pin, 0x44, 1)
|
|
-- wait a bit
|
|
tmr.alarm(0, delay or 100, 0, function()
|
|
-- iterate over devices
|
|
local r = { }
|
|
for i = 1, #d do
|
|
tmr.wdclr()
|
|
-- read rom command
|
|
ow.reset(pin)
|
|
ow.select(pin, d[i])
|
|
ow.write(pin, 0xBE, 1)
|
|
-- read data
|
|
local x = ow.read_bytes(pin, 9)
|
|
if ow.crc8(x) == 0 then
|
|
local t = (x:byte(1) + x:byte(2) * 256)
|
|
-- negatives?
|
|
if bit.isset(t, 15) then t = 1 - bit.bxor(t, 0xffff) end
|
|
-- NB: temperature in Celsius * 10^4
|
|
t = t * 625
|
|
-- NB: due 850000 means bad pullup. ignore
|
|
if t ~= 850000 then
|
|
r[format_addr(d[i])] = t
|
|
end
|
|
d[i] = nil
|
|
end
|
|
end
|
|
cb(r)
|
|
end)
|
|
end
|
|
-- expose
|
|
M = {
|
|
read = read,
|
|
}
|
|
end
|
|
return M
|