From a394808c328d2b8ed66db30974585c8d59b3e1ee Mon Sep 17 00:00:00 2001
From: Guido Günther <agx@sigxcpu.org>
Date: Thu, 28 Jan 2016 22:00:00 +0100
Subject: Initial commit

---
 src/w1therm.erl | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 src/w1therm.erl

(limited to 'src/w1therm.erl')

diff --git a/src/w1therm.erl b/src/w1therm.erl
new file mode 100644
index 0000000..a9810f3
--- /dev/null
+++ b/src/w1therm.erl
@@ -0,0 +1,43 @@
+%%% @author Guido Günther <agx@sigxcpu.org>
+%%% @copyright (C) 2016, Guido Günther
+%%% @doc
+%%% Read and write GPIO values from userspace
+%%%
+%%% @reference http://www.raspberrypi-spy.co.uk/2013/03/raspberry-pi-1-wire-digital-thermometer-sensor/
+%%% @end
+%%% License: LGLv3
+-module(w1therm).
+
+-define(W1_BASE, "/sys/bus/w1/devices/").
+
+-export([get_therms/0,
+         read_temp/1]).
+
+-type therm() :: string().
+
+% @doc: Get 1wire temperature famliy sensors
+-spec get_therms() -> {ok, list(therm())} | {error, atom()}.
+get_therms() ->
+    case file:list_dir(?W1_BASE) of
+        {error, enoent} -> {ok, []};
+        {error, Error} -> {error, Error};
+        {ok, Files} ->
+            {ok, R} = re:compile("^[0-9]{2}-.*"),
+            Names = [ X || X <- Files, nomatch /= re:run(X, R)],
+            {ok, Names}
+    end.
+
+% @doc: Read temperature from 1wire therm device in ⁰C
+-spec read_temp(Therm::therm()) -> {ok, float()} | {error, atom()}.
+read_temp(Therm) ->
+    Sysfs = therm_sysfs_path(Therm, w1_slave),
+    {ok, Data} = file:read_file(Sysfs),
+    Last = string:sub_word(binary:bin_to_list(Data), 2, $\n),
+    TempStr = string:sub_word(Last, 2, $=),
+    {Temp, []} = string:to_integer(TempStr),
+    {ok, Temp / 1000.0}.
+
+% private functions
+-spec therm_sysfs_path(Therm::therm(), atom() | binary()) -> string().
+therm_sysfs_path(Therm, File) ->
+    io_lib:format(?W1_BASE ++ Therm ++ "/~p", [File]).
-- 
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