tpetar
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Communicating With Multiple 1-Wire Devices
Original Web address : Dallas 1-Wire Projects With PicBasic Pro
Example:
OWOUT DQ, 1, [$33] ' Read ROM command, byte-sized data, reset before data
This will reset the 1-wire bus, [Send reset pulse before byte-sized data], and issue the byte-sized Read ROM command. This will work [only] if there is a single 1-wire device on the network. If there are more than a single 1-wire device on the network, we need to do the following:
Switch_1:
OWOUT DQ, 1, [$55,$05,$C5,$C3,$08,$00,$00,$00,$CD]' Match ROM, byte-sized, reset before
OWIN DQ, 4, [Stat]' Get bit-sized response, no reset pulse
IF Stat = 0 THEN
DEBUG Ins, Line2, "Switch #1 = OFF"
ELSE
DEBUG Ins, Line2, "Switch #1 = ON "
ENDIF
The example above shows how to individually address 1 DS2405 addressable 1-wire switch on the network. Notice we have substituted the Read ROM command with the Match ROM command. The red hexadecimal number $55 is the command for Match ROM. The blue hexadecimal numbers $05,$C5,$C3,$08,$00,$00,$00,$CD are the unique 64-bit ROM code numbers inside the specific DS2405 addressable 1-wire switch we're trying to communicate with.
What we're doing with --> OWOUT DQ, 1, [$55,$05,$C5,$C3,$08,$00,$00,$00,$CD]is: Attention, Match the following ROM code. Were leaving the 1-wire bus open for communications since we didn't RESET the 1-wire bus after we have sent several byte-sized data packets containing the ROM code. The device matching the ROM code [as shown in blue above], will respond if it's present on the 1-wire bus.
What we're doing with --> OWIN DQ, 4, [Stat]is: Reading the bit-sized data from the 1-wire bus into the bit-sized variable Stat, without issuing a reset pulse. The DS2405 will return a logic 0 on the 1-wire bus if its switch output PIO is ON or at logic 0. If the switch output is OFF, the DS2405 will return bit-sized data at logic 1, indicating to the Master controller that its switch output is OFF. Refer to the schematic at top again, and you'll notice that logic 0 will turn the NPN transistors OFF, and logic 1 will turn them ON again.
If you jumped into this page without reading the previous article showing how to read individual ROM codes from 1-wire components, visit this link HERE to see how this is done. You'll need to individually identify each of the 1-wire component unique 64-bit ROM codes before you can make sense of this article. Knowing the unique 64-bit ROM codes for all devices you're using [if you're building this project], is essential.
Let's move on to more of the mode switches, and see how they work with the DS18B20 temperature sensor on the 1-wire network.
Temp_1:
OWOUT DQ, 1, [$55,$28,$B1,$FE,$22,$00,$00,$00,$5D,$44]
W1:
OWIN DQ, 4, [Stat]' Check for still busy converting
IF Stat = 0 THEN W1' Still busy?, then loop
OWOUT DQ, 1,[$55,$28,$B1,$FE,$22,$00,$00,$00,$5D,$BE]
OWIN DQ, 2, [Temp.LOWBYTE,Temp.HIGHBYTE]' Read two bytes, then end communications
GOSUB Convert_Temp
DEBUG Ins,Line1, "Temp #1 = ", Sign, DEC (Temp / 100),".", DEC2 Temp, Deg, "F "
Notice from the code sample above that we have again issued the Match ROM command $55, and left the 1-wire bus open for communications. We next use mode 4 [bit-sized data, no reset pulse], and OWIN command to read the bit-sized response from the device addressed with the unique 64-bit ROM code $28,$B1,$FE,$22,$00,$00,$00,$5D.
Did you notice that the $44 is missing from end of the original first line of code? $44 is the last byte of data sent to the DS18B20 after the ROM code, and is telling the DS18B20 to begin a temperature conversion. I have made commands RED, and data BLUE for easy recognition.
What we're doing here --> OWIN DQ, 4, [Stat]: is reading the bit-sized response from the DS18B20. A logic 0 means the DS18B20 is still performing the temperature conversion, so we wait until it's finished before proceeding.
Notice how mode 4 allows us to read single-bit responses from the 1-wire bus without resetting the bus. This is important to remember if you're going to build a reliable 1-wire network. Sometimes the Master 1-wire controller will be required to read single-bit data, and be able to control [reset or no reset] the 1-wire bus as necessary. That's why it's important to carefully read the datasheet for any 1-wire device you're planning to use, and learn how to use the PicBasic Pro 1-wire command mode switches.
Original Web address : Dallas 1-Wire Projects With PicBasic Pro
Example:
OWOUT DQ, 1, [$33] ' Read ROM command, byte-sized data, reset before data
This will reset the 1-wire bus, [Send reset pulse before byte-sized data], and issue the byte-sized Read ROM command. This will work [only] if there is a single 1-wire device on the network. If there are more than a single 1-wire device on the network, we need to do the following:
Switch_1:
OWOUT DQ, 1, [$55,$05,$C5,$C3,$08,$00,$00,$00,$CD]' Match ROM, byte-sized, reset before
OWIN DQ, 4, [Stat]' Get bit-sized response, no reset pulse
IF Stat = 0 THEN
DEBUG Ins, Line2, "Switch #1 = OFF"
ELSE
DEBUG Ins, Line2, "Switch #1 = ON "
ENDIF
The example above shows how to individually address 1 DS2405 addressable 1-wire switch on the network. Notice we have substituted the Read ROM command with the Match ROM command. The red hexadecimal number $55 is the command for Match ROM. The blue hexadecimal numbers $05,$C5,$C3,$08,$00,$00,$00,$CD are the unique 64-bit ROM code numbers inside the specific DS2405 addressable 1-wire switch we're trying to communicate with.
What we're doing with --> OWOUT DQ, 1, [$55,$05,$C5,$C3,$08,$00,$00,$00,$CD]is: Attention, Match the following ROM code. Were leaving the 1-wire bus open for communications since we didn't RESET the 1-wire bus after we have sent several byte-sized data packets containing the ROM code. The device matching the ROM code [as shown in blue above], will respond if it's present on the 1-wire bus.
What we're doing with --> OWIN DQ, 4, [Stat]is: Reading the bit-sized data from the 1-wire bus into the bit-sized variable Stat, without issuing a reset pulse. The DS2405 will return a logic 0 on the 1-wire bus if its switch output PIO is ON or at logic 0. If the switch output is OFF, the DS2405 will return bit-sized data at logic 1, indicating to the Master controller that its switch output is OFF. Refer to the schematic at top again, and you'll notice that logic 0 will turn the NPN transistors OFF, and logic 1 will turn them ON again.
If you jumped into this page without reading the previous article showing how to read individual ROM codes from 1-wire components, visit this link HERE to see how this is done. You'll need to individually identify each of the 1-wire component unique 64-bit ROM codes before you can make sense of this article. Knowing the unique 64-bit ROM codes for all devices you're using [if you're building this project], is essential.
Let's move on to more of the mode switches, and see how they work with the DS18B20 temperature sensor on the 1-wire network.
Temp_1:
OWOUT DQ, 1, [$55,$28,$B1,$FE,$22,$00,$00,$00,$5D,$44]
W1:
OWIN DQ, 4, [Stat]' Check for still busy converting
IF Stat = 0 THEN W1' Still busy?, then loop
OWOUT DQ, 1,[$55,$28,$B1,$FE,$22,$00,$00,$00,$5D,$BE]
OWIN DQ, 2, [Temp.LOWBYTE,Temp.HIGHBYTE]' Read two bytes, then end communications
GOSUB Convert_Temp
DEBUG Ins,Line1, "Temp #1 = ", Sign, DEC (Temp / 100),".", DEC2 Temp, Deg, "F "
Notice from the code sample above that we have again issued the Match ROM command $55, and left the 1-wire bus open for communications. We next use mode 4 [bit-sized data, no reset pulse], and OWIN command to read the bit-sized response from the device addressed with the unique 64-bit ROM code $28,$B1,$FE,$22,$00,$00,$00,$5D.
Did you notice that the $44 is missing from end of the original first line of code? $44 is the last byte of data sent to the DS18B20 after the ROM code, and is telling the DS18B20 to begin a temperature conversion. I have made commands RED, and data BLUE for easy recognition.
What we're doing here --> OWIN DQ, 4, [Stat]: is reading the bit-sized response from the DS18B20. A logic 0 means the DS18B20 is still performing the temperature conversion, so we wait until it's finished before proceeding.
Notice how mode 4 allows us to read single-bit responses from the 1-wire bus without resetting the bus. This is important to remember if you're going to build a reliable 1-wire network. Sometimes the Master 1-wire controller will be required to read single-bit data, and be able to control [reset or no reset] the 1-wire bus as necessary. That's why it's important to carefully read the datasheet for any 1-wire device you're planning to use, and learn how to use the PicBasic Pro 1-wire command mode switches.
