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DS18B20 - CRC check added to lua module, minor optimization; change of ow module example #2992

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Jan 2, 2020
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DS18B20 - CRC check added to lua module, minor optimization; change of ow module example #2992

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60 changes: 27 additions & 33 deletions docs/modules/ow.md
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Original file line number Diff line number Diff line change
Expand Up @@ -145,48 +145,42 @@ Issues a 1-Wire rom select command. Make sure you do the `ow.reset(pin)` first.
#### Example
```lua
-- 18b20 Example
pin = 9
-- 18b20 Example
pin = 3
ow.setup(pin)
count = 0
repeat
count = count + 1
addr = ow.reset_search(pin)
addr = ow.search(pin)
tmr.wdclr()
until (addr ~= nil) or (count > 100)
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addr = ow.reset_search(pin)
addr = ow.search(pin)

if addr == nil then
print("No more addresses.")
print("No device detected.")
else
print(addr:byte(1,8))
crc = ow.crc8(string.sub(addr,1,7))
local crc = ow.crc8(string.sub(addr,1,7))
if crc == addr:byte(8) then
if (addr:byte(1) == 0x10) or (addr:byte(1) == 0x28) then
print("Device is a DS18S20 family device.")
repeat
tmr.create():alarm(1000, tmr.ALARM_AUTO, function()
ow.reset(pin)
ow.select(pin, addr)
ow.write(pin, 0x44, 1)
tmr.delay(1000000)
present = ow.reset(pin)
ow.select(pin, addr)
ow.write(pin,0xBE,1)
print("P="..present)
data = nil
data = string.char(ow.read(pin))
for i = 1, 8 do
data = data .. string.char(ow.read(pin))
end
print(data:byte(1,9))
crc = ow.crc8(string.sub(data,1,8))
print("CRC="..crc)
if crc == data:byte(9) then
t = (data:byte(1) + data:byte(2) * 256) * 625
t1 = t / 10000
t2 = t % 10000
print("Temperature="..t1.."."..t2.."Centigrade")
end
tmr.wdclr()
until false
ow.write(pin, 0x44, 1) -- convert T command
tmr.create():alarm(750, tmr.ALARM_SINGLE, function()
ow.reset(pin)
ow.select(pin, addr)
ow.write(pin,0xBE,1) -- read scratchpad command
local data = ow.read_bytes(pin, 9)
print(data:byte(1,9))
local crc = ow.crc8(string.sub(data,1,8))
print("CRC="..crc)
if crc == data:byte(9) then
local t = (data:byte(1) + data:byte(2) * 256) * 625
local sgn = t<0 and -1 or 1
local tA = sgn*t
local t1 = math.floor(tA / 10000)
local t2 = tA % 10000
print("Temperature="..(sgn<0 and "-" or "")..t1.."."..t2.." Centigrade")
end
end)
end)
else
print("Device family is not recognized.")
end
Expand Down
30 changes: 17 additions & 13 deletions lua_modules/ds18b20/ds18b20.lua
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Expand Up @@ -69,6 +69,7 @@ local function readout(self)
-- the DS18B20 family has 4 fractional bits and the DS18S20s, 1 fractional bit
t = ((t <= 32767) and t or t - 65536) *
((addr:byte(1) == DS18B20FAMILY) and 625 or 5000)
local crc, b9 = ow_crc8(string.sub(data,1,8)), data:byte(9)

if 1/2 == 0 then
-- integer version
Expand All @@ -83,22 +84,22 @@ local function readout(self)
local tL=(tA%10000)/1000 + ((tA%1000)/100 >= 5 and 1 or 0)

if tH and (t~=850000) then
temp[addr]=(sgn<0 and "-" or "")..tH.."."..tL
debugPrint(to_string(addr),(sgn<0 and "-" or "")..tH.."."..tL)
debugPrint(to_string(addr),(sgn<0 and "-" or "")..tH.."."..tL, crc, b9)
if crc==b9 then temp[addr]=(sgn<0 and "-" or "")..tH.."."..tL end
status[i] = 2
end
-- end integer version
else
-- float version
if t and (math_floor(t/10000)~=85) then
t = t / 10000
t = t / 10000
if math_floor(t)~=85 then
if unit == 'F' then
t = t * 18/10 + 32
elseif unit == 'K' then
t = t + 27315/100
end
self.temp[addr]=t
debugPrint(to_string(addr), t)
debugPrint(to_string(addr), t, crc, b9)
if crc==b9 then temp[addr]=t end
status[i] = 2
end
-- end float version
Expand All @@ -123,19 +124,22 @@ conversion = (function (self)
if powered_only then
debugPrint("starting conversion: all sensors")
ow_reset(pin)
ow_skip(pin) -- select the sensor
ow_skip(pin) -- skip ROM selection, talk to all sensors
ow_write(pin, CONVERT_T, MODE) -- and start conversion
for i, _ in ipairs(sens) do status[i] = 1 end
else
local started = false
for i, s in ipairs(sens) do
if status[i] == 0 then
local addr, parasite = s:sub(1,8), s:byte(9)
debugPrint("starting conversion:", to_string(addr), parasite == 1 and "parasite" or " ")
local addr, parasite = s:sub(1,8), s:byte(9) == 1
if parasite and started then break end -- do not start concurrent conversion of powered and parasite
debugPrint("starting conversion:", to_string(addr), parasite and "parasite" or "")
ow_reset(pin)
ow_select(pin, addr) -- select the sensor
ow_write(pin, CONVERT_T, MODE) -- and start conversion
status[i] = 1
if parasite == 1 then break end -- parasite sensor blocks bus during conversion
if parasite then break end -- parasite sensor blocks bus during conversion
started = true
end
end
end
Expand Down Expand Up @@ -169,16 +173,16 @@ local function _search(self, lcb, lpin, search, save)
for i, _ in ipairs(sens) do status[i] = 0 end
end
local function cycle()
debugPrint("cycle")
if addr then
local crc=ow_crc8(addr:sub(1,7))
if (crc==addr:byte(8)) and ((addr:byte(1)==DS1920FAMILY) or (addr:byte(1)==DS18B20FAMILY)) then
ow_reset(pin)
ow_select(pin, addr)
ow_write(pin, READ_POWERSUPPLY, MODE)
local parasite = (ow_read(pin)==0 and 1 or 0)
sens[#sens+1]= addr..string_char(parasite) -- {addr=addr, parasite=parasite, status=0}
debugPrint("contact: ", to_string(addr), parasite == 1 and "parasite" or " ")
sens[#sens+1]= addr..string_char(parasite)
status[#sens] = 0
debugPrint("contact: ", to_string(addr), parasite == 1 and "parasite" or "")
end
addr = ow_search(pin)
node_task_post(node_task_LOW_PRIORITY, cycle)
Expand Down