From 9bc9955e2c8436dfee063b0c1106c6a07838a961 Mon Sep 17 00:00:00 2001
From: Nat Lasseter <user@4574.co.uk>
Date: Mon, 8 Jul 2024 10:49:56 +0100
Subject: Add sds.rb

---
 README |  2 ++
 sds.rb | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)
 create mode 100755 sds.rb

diff --git a/README b/README
index 7b963dc..4eb937a 100644
--- a/README
+++ b/README
@@ -27,6 +27,8 @@ pdfbook4.rb:
   Page order to make (or pdfjam command to turn a pdf file into) 4-up double-sided brochure ordered pages (to make two A6 folia per A4 page)
 scan.sh:
   Batch scanning script
+sds.rb:
+  Read streaming data from an SDS011
 section.c:
   Like the section command on IOS
 slide.rb:
diff --git a/sds.rb b/sds.rb
new file mode 100755
index 0000000..c28d508
--- /dev/null
+++ b/sds.rb
@@ -0,0 +1,66 @@
+#!/usr/bin/env ruby
+
+class Rdr
+  def initialize(f)
+    @f = f
+    reset
+  end
+
+  def valid?
+    @len == 10# && @csok
+  end
+
+  def read!
+    v = @f.read(1)
+    @len += 1
+
+    case @len
+    when 1
+      reset if v != 0xAA
+    when 2
+      reset if v != 0xC0
+    when 3
+      @pm25 = v
+    when 4
+      @pm25 += v * 256
+    when 5
+      @pm10 = v
+    when 6
+      @pm10 += v * 256
+    when 7
+      @id = v
+    when 8
+      @id += v * 256
+    when 9
+      if checksum == v
+        @csok = true
+      else
+        reset
+      end
+    when 10
+      reset if v != 0xAB
+    else
+      reset
+    end
+  end
+
+  def checksum
+    ((@pm25 / 256) + (@pm25 % 256) +
+     (@pm10 / 256) + (@pm10 % 256) +
+     (@id   / 256) + (@id   % 256)) % 256
+  end
+
+  def reset
+    @len = 0
+    @pm25 = 0
+    @pm10 = 0
+    @id = 0
+    @csok = false
+  end
+end
+
+File.open("/dev/ttyUSB0", "rb") do |f|
+  r = Rdr.new(f)
+  r.read! until r.valid?
+  puts "Hooray"
+end
-- 
cgit v1.2.1