Matrix Orbital LK402-25 - Manual (Page 29)

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5. Dallas One-Wire
5.1. Search for a One-Wire
Device
Dec
Hex 254 200 2
FE C8 02
Sends a search query to each of the up to 32 devices on the one wire bus. Any connected device will respond with
an identification packet.
Response 14 bytes, identification packet as shown below
Table 23: Dallas One-Wire Packet Information
Offset Length Value Description
0 2 9002 Preamble
2 1 138 Another device packet will follow OR
10 Last device packet
3 1 49 Packet Type
4 1 0 Error Code (0 indicates success)
5 8 Device Address
13 1 0 CRC8 address check (0 indicates validity)
5.2. Dallas One-Wire
Transaction
Dec
Hex 254 200 1
FE C8 01
Flags Send Bits Receive Bits Data
Flags Send Bits Receive Bits Data
Performs a single Dallas 1-Wire transaction. Consult your device documentation for information regarding device
specific protocols. If an error is encountered, a corresponding value will be returned by the device.
Flags 1 byte, flags for transaction, see below
Send Bits 1 byte, number of bytes to be sent to the device
Receive Bits 1 byte, number of bytes expected to be received from the device
Data Variable, data to be transmitted LSB to MSB
Table 24: Dallas One-Wire Flag Table
Bit Flag Description
7
6 Unused
5
4 0 (Future Compatibility)
3 Add CRC8 to transaction
2 0 (Future Compatibility)
1 Read CRC8 from transaction
0 Reset Bus prior to transaction
Table 25: Dallas One-Wire Error Table
Code Error Description
0 Success
1 Unknown Command
2 No Devices Found
3 Fatal Search Error