From 87d61960d7c15084aebffe28b1dea87dc7b716c8 Mon Sep 17 00:00:00 2001
From: Daniel Friesel <derf@finalrewind.org>
Date: Wed, 20 Apr 2022 19:11:35 +0200
Subject: initial commit

---
 scd4x.lua | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 scd4x.lua

(limited to 'scd4x.lua')

diff --git a/scd4x.lua b/scd4x.lua
new file mode 100644
index 0000000..47495e2
--- /dev/null
+++ b/scd4x.lua
@@ -0,0 +1,45 @@
+local scd4x = {}
+local device_address = 0x62
+
+scd4x.bus_id = 0
+
+function scd4x.start()
+	i2c.start(scd4x.bus_id)
+	if not i2c.address(scd4x.bus_id, device_address, i2c.TRANSMITTER) then
+		return false
+	end
+	i2c.write(scd4x.bus_id, {0x21, 0xb1})
+	i2c.stop(scd4x.bus_id)
+	return true
+end
+
+function scd4x.stop()
+	i2c.start(scd4x.bus_id)
+	if not i2c.address(scd4x.bus_id, device_address, i2c.TRANSMITTER) then
+		return false
+	end
+	i2c.write(scd4x.bus_id, {0x3f, 0x86})
+	i2c.stop(scd4x.bus_id)
+	return true
+end
+
+function scd4x.read()
+	i2c.start(scd4x.bus_id)
+	if not i2c.address(scd4x.bus_id, device_address, i2c.TRANSMITTER) then
+		return nil
+	end
+	i2c.write(scd4x.bus_id, {0xec, 0x05})
+	i2c.stop(scd4x.bus_id)
+	i2c.start(scd4x.bus_id)
+	if not i2c.address(scd4x.bus_id, device_address, i2c.RECEIVER) then
+		return nil
+	end
+	local data = i2c.read(scd4x.bus_id, 9)
+	i2c.stop(scd4x.bus_id)
+	local co2 = string.byte(data, 1) * 256 + string.byte(data, 2)
+	local temp_raw = 175 * (string.byte(data, 4) * 256 + string.byte(data, 5))
+	local humi_raw = 100 * (string.byte(data, 7) * 256 + string.byte(data, 8))
+	return co2, temp_raw, humi_raw
+end
+
+return scd4x
-- 
cgit v1.2.3