- Sat Jul 25, 2015 9:51 am
#24235
Hey guys, total LUA noob here.
I've written a module for SHT-11, feel free to use it and comment on it.
Attached is the module and an example script on how to use it.
Cheers!
SHT-11 module:
Usage example:
I've written a module for SHT-11, feel free to use it and comment on it.
Attached is the module and an example script on how to use it.
Cheers!
SHT-11 module:
Code: Select all
local moduleName = ...
local M = {}
_G[moduleName] = M
--table module
local table = table
--bit module
local bit = bit
--timer module
local tmr = tmr
--gpio module
local gpio = gpio
-- local environoment
setfenv(1, M)
local function set_sck(v)
if (v == 1) then
gpio.write(sck, gpio.HIGH)
else
gpio.write(sck, gpio.LOW)
end
end
local function set_data(v)
if (v == 1) then
gpio.mode(data, gpio.INPUT)
else
gpio.write(data, gpio.LOW)
gpio.mode(data, gpio.OUTPUT)
end
end
local function start()
set_data(1)
set_sck(0)
tmr.delay(1)
set_sck(1)
tmr.delay(1)
set_data(0)
tmr.delay(1)
set_sck(0)
tmr.delay(1)
set_sck(1)
tmr.delay(1)
set_data(1)
tmr.delay(1)
set_sck(0)
end
local function reset()
set_data(1)
set_sck(0)
for i = 0, 8 do
set_sck(1)
tmr.delay(1)
set_sck(0)
tmr.delay(1)
end
start()
end
local function write(v)
local c = v
local ret
for i = 0, 7 do
if (bit.band(c, 0x80) ~= 0) then
set_data(1)
else
set_data(0)
end
c = bit.lshift(c, 1)
set_sck(1)
tmr.delay(1)
set_sck(0)
tmr.delay(1)
end
set_data(1)
set_sck(1)
tmr.delay(1)
ret = gpio.read(data)
set_sck(0)
return ret
end
local function read(ack)
local c = 0
set_data(1)
for i = 0, 7 do
c = bit.lshift(c, 1)
set_sck(1)
tmr.delay(1)
c = bit.bor(c, gpio.read(data))
set_sck(0)
tmr.delay(1)
end
if (ack == 1) then
set_data(0)
end
set_sck(1)
tmr.delay(1)
set_sck(0)
set_data(1)
return c
end
function M.init(s, d)
sck = s
data = d
gpio.mode(data, gpio.INPUT);
gpio.mode(sck, gpio.OUTPUT);
end
function M.read_measurements()
reset()
start()
--TODO: add ACK check
write(0x03)
set_data(1)
--TODO: add timeout
for i = 0, 65536 do
if (gpio.read(data) == 0) then
break
end
end
t0 = read(1)
t1 = read(1)
--TODO: add crc checking
t_crc = read(0)
t = bit.lshift(t0, 8);
t = bit.bor(t, t1)
--t = t - 4010 --for 5V
t = t - 3970 --for 3.5V
start()
write(0x05)
set_data(1)
--TODO: add timeout
for i = 0, 65536 do
if (gpio.read(data) == 0) then
break
end
end
h0 = read(1)
h1 = read(1)
--TODO: add crc checking
h_crc = read(0)
h = bit.lshift(h0, 8);
h = bit.bor(h, h1)
--compensation magic part 1
rh = 268 * h
rh = rh / 256
rh = -rh
rh = rh + 24052
rh = rh * h
rh = rh - 1341391
rh = rh / 65536
--compensation magic part 2
rh_true = 52 * h
rh_true = 6554 + rh_true
rh_true = rh_true * (t - 2500) / 100
rh_true = rh_true / 65536
rh_true = rh_true + rh
return t, rh_true
end
return M
Usage example:
Code: Select all
sht = require("sht11")
--clock on GPIO4, data on GPIO12
sht.init(2, 6)
t, h = sht.read_measurements()
print("Temp: " .. t / 100 .. "." .. t % 100)
print("Hum: " .. h / 10 .. "." .. h % 10 .. " %")
