313 lines
8.1 KiB
Markdown
313 lines
8.1 KiB
Markdown
# 1-Wire Module
|
|
| Since | Origin / Contributor | Maintainer | Source |
|
|
| :----- | :-------------------- | :---------- | :------ |
|
|
| 2014-12-22 | [Zeroday](https://github.com/funshine) | [Zeroday](https://github.com/funshine) | [ow.c](../../app/modules/ow.c)|
|
|
|
|
This module provides functions to work with the [1-Wire](https://en.wikipedia.org/wiki/1-Wire) device communications bus system.
|
|
|
|
## ow.check_crc16()
|
|
Computes the 1-Wire CRC16 and compare it against the received CRC.
|
|
|
|
#### Syntax
|
|
`ow.check_crc16(buf, inverted_crc0, inverted_crc1[, crc])`
|
|
|
|
#### Parameters
|
|
- `buf` string value, data to be calculated check sum in string
|
|
- `inverted_crc0` LSB of received CRC
|
|
- `inverted_crc1` MSB of received CRC
|
|
- `crc` CRC starting value (optional)
|
|
|
|
#### Returns
|
|
true if the CRC matches, false otherwise
|
|
|
|
## ow.crc16()
|
|
Computes a Dallas Semiconductor 16 bit CRC. This is required to check the integrity of data received from many 1-Wire devices. Note that the CRC computed here is **not** what you'll get from the 1-Wire network, for two reasons:
|
|
|
|
1. The CRC is transmitted bitwise inverted.
|
|
2. Depending on the endian-ness of your processor, the binary representation of the two-byte return value may have a different byte order than the two bytes you get from 1-Wire.
|
|
|
|
#### Syntax
|
|
`ow.crc16(buf[, crc])`
|
|
|
|
#### Parameters
|
|
- `buf` string value, data to be calculated check sum in string
|
|
- `crc` CRC starting value (optional)
|
|
|
|
#### Returns
|
|
the CRC16 as defined by Dallas Semiconductor
|
|
|
|
## ow.crc8()
|
|
Computes a Dallas Semiconductor 8 bit CRC, these are used in the ROM and scratchpad registers.
|
|
|
|
#### Syntax
|
|
`ow.crc8(buf)`
|
|
|
|
#### Parameters
|
|
`buf` string value, data to be calculated check sum in string
|
|
|
|
#### Returns
|
|
CRC result as byte
|
|
|
|
## ow.depower()
|
|
Stops forcing power onto the bus. You only need to do this if you used the 'power' flag to `ow.write()` or used a `ow.write_bytes()` and aren't about to do another read or write.
|
|
|
|
#### Syntax
|
|
`ow.depower(pin)`
|
|
|
|
#### Parameters
|
|
`pin` 1~12, I/O index
|
|
|
|
#### Returns
|
|
`nil`
|
|
|
|
#### See also
|
|
- [ow.write()](#owwrite)
|
|
- [ow.write_bytes()](#owwrite_bytes)
|
|
|
|
## ow.read()
|
|
Reads a byte.
|
|
|
|
#### Syntax
|
|
`ow.read(pin)`
|
|
|
|
#### Parameters
|
|
`pin` 1~12, I/O index
|
|
|
|
#### Returns
|
|
byte read from slave device
|
|
|
|
## ow.read_bytes()
|
|
Reads multi bytes.
|
|
|
|
#### Syntax
|
|
`ow.read_bytes(pin, size)`
|
|
|
|
#### Parameters
|
|
- `pin` 1~12, I/O index
|
|
- `size` number of bytes to be read from slave device (up to 256)
|
|
|
|
#### Returns
|
|
`string` bytes read from slave device
|
|
|
|
## ow.reset()
|
|
Performs a 1-Wire reset cycle.
|
|
|
|
#### Syntax
|
|
`ow.reset(pin)`
|
|
|
|
#### Parameters
|
|
`pin` 1~12, I/O index
|
|
|
|
#### Returns
|
|
- `1` if a device responds with a presence pulse
|
|
- `0` if there is no device or the bus is shorted or otherwise held low for more than 250 µS
|
|
|
|
## ow.reset_search()
|
|
Clears the search state so that it will start from the beginning again.
|
|
|
|
#### Syntax
|
|
`ow.reset_search(pin)`
|
|
|
|
#### Parameters
|
|
`pin` 1~12, I/O index
|
|
|
|
#### Returns
|
|
`nil`
|
|
|
|
## ow.search()
|
|
Looks for the next device.
|
|
|
|
#### Syntax
|
|
`ow.search(pin, [alarm_search])`
|
|
|
|
#### Parameters
|
|
- `pin` 1~12, I/O index
|
|
- `alarm_search` 1 / 0, if 0 a regular 0xF0 search is performed (default if parameter is absent), if 1 a 0xEC ALARM SEARCH is performed.
|
|
|
|
#### Returns
|
|
`rom_code` string with length of 8 upon success. It contains the rom code of slave device. Returns `nil` if search was unsuccessful.
|
|
|
|
#### See also
|
|
[ow.target_search()](#owtargetsearch)
|
|
|
|
## ow.select()
|
|
Issues a 1-Wire rom select command. Make sure you do the `ow.reset(pin)` first.
|
|
|
|
#### Syntax
|
|
`ow.select(pin, rom)`
|
|
|
|
#### Parameters
|
|
- `pin` 1~12, I/O index
|
|
- `rom` string value, len 8, rom code of the slave device
|
|
|
|
#### Returns
|
|
`nil`
|
|
|
|
#### Example
|
|
```lua
|
|
-- 18b20 Example
|
|
-- 18b20 Example
|
|
pin = 3
|
|
ow.setup(pin)
|
|
addr = ow.reset_search(pin)
|
|
addr = ow.search(pin)
|
|
|
|
if addr == nil then
|
|
print("No device detected.")
|
|
else
|
|
print(addr:byte(1,8))
|
|
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.")
|
|
tmr.create():alarm(1000, tmr.ALARM_AUTO, function()
|
|
ow.reset(pin)
|
|
ow.select(pin, addr)
|
|
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
|
|
else
|
|
print("CRC is not valid!")
|
|
end
|
|
end
|
|
```
|
|
|
|
#### See also
|
|
[ow.reset()](#owreset)
|
|
|
|
## ow.setup()
|
|
Sets a pin in onewire mode.
|
|
|
|
#### Syntax
|
|
`ow.setup(pin)`
|
|
|
|
#### Parameters
|
|
`pin` 1~12, I/O index
|
|
|
|
#### Returns
|
|
`nil`
|
|
|
|
## ow.skip()
|
|
Issues a 1-Wire rom skip command, to address all on bus.
|
|
|
|
#### Syntax
|
|
`ow.skip(pin)`
|
|
|
|
#### Parameters
|
|
`pin` 1~12, I/O index
|
|
|
|
#### Returns
|
|
`nil`
|
|
|
|
## ow.target_search()
|
|
Sets up the search to find the device type `family_code`. The search itself has to be initiated with a subsequent call to `ow.search()`.
|
|
|
|
#### Syntax
|
|
`ow.target_search(pin, family_code)`
|
|
|
|
#### Parameters
|
|
- `pin` 1~12, I/O index
|
|
- `family_code` byte for family code
|
|
|
|
#### Returns
|
|
`nil`
|
|
|
|
#### See also
|
|
[ow.search()](#owsearch)
|
|
|
|
## ow.write()
|
|
Writes a byte. If `power` is 1 then the wire is held high at the end for parasitically powered devices. You are responsible for eventually depowering it by calling `ow.depower()` or doing another read or write.
|
|
|
|
#### Syntax
|
|
`ow.write(pin, v, power)`
|
|
|
|
#### Parameters
|
|
- `pin` 1~12, I/O index
|
|
- `v` byte to be written to slave device
|
|
- `power` 1 for wire being held high for parasitically powered devices
|
|
|
|
#### Returns
|
|
`nil`
|
|
|
|
#### See also
|
|
[ow.depower()](#owdepower)
|
|
|
|
## ow.write_bytes()
|
|
Writes multi bytes. If `power` is 1 then the wire is held high at the end for parasitically powered devices. You are responsible for eventually depowering it by calling `ow.depower()` or doing another read or write.
|
|
|
|
#### Syntax
|
|
`ow.write_bytes(pin, buf, power)`
|
|
|
|
#### Parameters
|
|
- `pin` 1~12, IO index
|
|
- `buf` string to be written to slave device
|
|
- `power` 1 for wire being held high for parasitically powered devices
|
|
|
|
#### Returns
|
|
`nil`
|
|
|
|
#### See also
|
|
[ow.depower()](#owdepower)
|
|
|
|
## ow.set_timings()
|
|
Tweak different bit timing parameters. Some slow custom devices might not work perfectly well with NodeMCU as 1-wire master. Since NodeMCU ow module is bit-banging the 1-wire protocol, it is possible to adjust the timings a bit.
|
|
|
|
Note that you can break the protocol totally if you tweak some numbers too much. This should never be needed with normal devices.
|
|
|
|
#### Syntax
|
|
`ow.set_timings(reset_tx, reset_wait, reset_rx, w1_low, w1_high, w0_low, w0_high, r_low, r_wait, r_delay)`
|
|
|
|
#### Parameters
|
|
Each parameter specifies number of microseconds to delay at different stages in the 1-wire bit-banging process.
|
|
A nil value will leave the value unmodified.
|
|
|
|
- `reset_tx` pull bus low during reset (default 480)
|
|
- `reset_wait` wait for presence pulse after reset (default 70)
|
|
- `reset_rx` delay after presence pulse have been checked (default 410)
|
|
- `w1_low` pull bus low during write 1 slot (default 5)
|
|
- `w1_high` leave bus high during write 1 slot (default 52)
|
|
- `w0_low` pull bus low during write 1 slot (default 65)
|
|
- `w0_high` leave bus high during write 1 slot (default 5)
|
|
- `r_low` pull bus low during read slot (default 5)
|
|
- `r_wait` wait before reading bus level during read slot (default 8)
|
|
- `r_delay` delay after reading bus level (default 52)
|
|
|
|
#### Returns
|
|
`nil`
|
|
|
|
#### Example
|
|
```lua
|
|
-- Give 300uS longer read/write slots for slow MCU based 1-wire slave
|
|
ow.set_timings(
|
|
nil, -- reset_tx
|
|
nil, -- reset_wait
|
|
nil, -- reset_rx
|
|
nil, -- w1_low
|
|
352, -- w1_high
|
|
nil, -- w0_low
|
|
305, -- w0_high
|
|
nil, -- r_low
|
|
nil, -- r_wait
|
|
352 -- r_delay
|
|
)
|
|
```
|