Difference between revisions of "Component: One Wire (Comms: Interface)"
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*[[Component:_Temperature_(DS18B20)_(Environmental)|DS18B20 Temperature Sensor]] | *[[Component:_Temperature_(DS18B20)_(Environmental)|DS18B20 Temperature Sensor]] | ||
*[[Component:_Temperature_(DS18S20)_(Environmental)|DS18S20 Temperature Sensor]] | *[[Component:_Temperature_(DS18S20)_(Environmental)|DS18S20 Temperature Sensor]] | ||
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==Downloadable macro reference== | ==Downloadable macro reference== | ||
Revision as of 14:49, 13 August 2021
| Author | Matrix Ltd |
| Version | 1.3 (Release) |
| Category | Comms: Interface |
Contents
One Wire component
Low level routines for controlling or interacting with a standard one wire interface.
Examples
Device Scanning
To get started with one wire devices it is often useful to collect the unique device serial number for each and every one wire device you are going to connect to your bus.
For example if you have a bus with two temperature sensors connected it is useful to know which sensor is which. Sensor A is monitoring temperature A and sensor B is monitoring temperature B. The only way to tell which is which is to use the serial number.
Here is a program that scans for devices on a one wire bus and outputs the device count and serial numbers using a LCD.
Here is the same program but this time the device count and serial numbers are output using a UART such as on an Arduino or ESP32.
To use the examples simply connect a single device to the one wire bus and make a note of the reported serial number.
This serial number can then be entered into the specific one wire component and used to ensure you are communicating with the device you think you are.
A pull up resistor of between 1K and 10K is required between the data I/O pin and VCC.
Further Examples
The One Wire component is a key building block required by a number of other components. Some of which are included below.
Downloadable macro reference
ReceiveByte
Receives a byte from the one wire bus a bit at a time
Parameters
- This macro has no parameters
Return value
WriteScratchpad
Writes to the scratchpad for the selected device.
Must be called after a MatchROM macro call.
Parameters
- BYTE Data
- BYTE Count
Return value
- This call does not return a value
TransmitByte
Transmit a byte to the one wire bus a bit at a time
Parameters
- BYTE Command
Return value
- This call does not return a value
SkipROM
Performs a bus reset and the sends the SkipROM command byte
Parameters
- This macro has no parameters
Return value
- This call does not return a value
BusReset
Issue a 'ping' on the bus. If there is at least one sensor on the bus then it will generate a presence pulse.
Returns 0 if a presense pulse was detected
Returns 1 no device was detected
Parameters
- This macro has no parameters
Return value
- BOOL : Returns true if the operation is a success, else false
MatchROM
Performs a reset followed by the MatchROM code and then the 8-bit ROM code.
Parameters
- BYTE FamilyCode
- BYTE SerialNumber
Return value
- This call does not return a value
ReadScratchpad
Reads the 9-Byte scratchpad for the selected device.
Must be called after a MatchROM macro call.
Parameters
- This macro has no parameters
Return value
- This call does not return a value
ScanBus
Scans the one wire bus to detect all connected devices.
Returns the number of one wire devices found.
Parameters
- This macro has no parameters
Return value
GetDeviceCount
Returns the number of devices found by the last ScanBus operation.
Parameters
- This macro has no parameters
Return value
GetScratchpadByte
Returns a byte from the last read scratchpad at position index.
The index byte can go from 0 - 8 to reference the 9 individual scratchpad bytes.
Parameters
- BYTE Index
- Select which pad byte to use 0-8
Return value
GetIDByte
Returns byte ectet of the 64-Bit lasered ROM code, 255 on error
Parameters
- BYTE Device
- Device ID - Range: 0 - NumDevices - 1
- BYTE ByteIndex
- Index of the data byte. 0=FamilyCode, 1-6=Serial, 7=CRC
Return value
Initialise
Sets up the 1-Wire output pin ready for communications.
Parameters
- This macro has no parameters
Return value
- This call does not return a value
Simulation macro reference
This component does not contain any simulation macros
Property reference
One Wire Pin
This property is of type Single digital pin and can be referenced with the variable name oo_pin.
I/O pin used to host one wire bus.
Timing
This property is of type Fixed list of ints and can be referenced with the variable name Timing.
Sets the component timing model.
Standard is the usual 1-wire timing,
Overdrive is a high speed 1-wire timing.
Max Devices
This property is of type Unsigned integer and can be referenced with the variable name BufferSize.
Controls the maximum number of devices that can be detected during a ScanBus.
For each additional device we require 8 bytes to store the ROM ID.
Default: 8 = 64 Bytes of RAM
