yet another ds18b20 module added

lua_examples/yet-another-ds18b20.lua

@@ -0,0 +1,65 @@
+------------------------------------------------------------------------------
+-- DS18B20 query module
+--
+-- LICENCE: http://opensource.org/licenses/MIT
+-- Vladimir Dronnikov <dronnikov@gmail.com>
+--
+-- Example:
+-- for k, v in pairs(require("ds18b20").read(4)) do print(k, v) end
+------------------------------------------------------------------------------
+local M
+do
+  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, 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.delay(delay or 100000)
+    -- 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) * 625
+        -- NB: temperature in Celcius * 10^4
+        r[format_addr(d[i])] = t
+        d[i] = nil
+      end
+    end
+    return r
+  end
+  -- expose
+  M = {
+    read = read,
+  }
+end
+return M