Post by thread:[PIC]: DS18S20 addressing individual devices

Hello all, I've built a small project which uses one 18S20, which works well. I am now trying to write a routine to get the serial numbers of a number of devices connected to the 1 wire bus. I'm using C has anyone written some code they are prepared to share, or can you point me to a good source/webpage ? Tony Nixon wrote: {Quote hidden}> Hi all, > > I've been putting together a small data logger application that uses 4 > of the DS18S20 1 wire temp sensors, a Honeywell humidity sensor and two > electronic scales that I talk to with bit banged RS232 code. I then > relay the results to the PC via the UART, or just store to local I2C > memory for portabillity. > > The data sheet says 750mS to get each temp conversion and some people > here want to use the logger with more temp sensors. The trouble is the > acquisition time goes up substantially and you can't really say that the > temps were all logged at exactly X time. > > Is there any way around this that anyone knows of. > > Assuming someone knows the DS18S20, I was wondering if you could use a > bypass ROM command and start the conversions all together, and then read > individually after just a single 750mS conversion??? > > -- > Best regards > > Tony > > mICros > http://www.bubblesoftonline.com > spam_OUTsalesTakeThisOuTbubblesoftonline.com > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Steven Allard wrote: > > Hello all, > > I've built a small project which uses one 18S20, which works well. I am now > trying to write a routine to get the serial numbers of a number of devices > connected to the 1 wire bus. > > I'm using C has anyone written some code they are prepared to share, or can > you point me to a good source/webpage ? This is in assembler, but perhaps you can port it to C without much bother. Data in buffer after execution = 8 bytes Family Code - 1 byte ID Number - 6 bytes CRC - 1 Byte movlw Buffer ; set buffer pointer movwf FSR call INITDS ; start new transaction Send_Out Read_ROM ; read ROM command GIDLoop call IN_BYTE ; read bytes movwf INDF incf FSR movlw Buffer + d'8' xorwf FSR,W btfss STATUS,Z goto GIDLoop return -- Best regards Tony mICros http://www.bubblesoftonline.com .....salesKILLspam@spam@bubblesoftonline.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

Tony Nixon wrote: I forgot to mention that this will only work for 1 device on the bus at a time. There is a much more complicated procedure to use if multiple devices are on the bus and need identification, but I haven't used that method yet. {Quote hidden}> This is in assembler, but perhaps you can port it to C without much > bother. > > Data in buffer after execution = 8 bytes > > Family Code - 1 byte > ID Number - 6 bytes > CRC - 1 Byte > > movlw Buffer ; set buffer pointer > movwf FSR > call INITDS ; start new transaction > Send_Out Read_ROM ; read ROM command > GIDLoop call IN_BYTE ; read bytes > movwf INDF > incf FSR > movlw Buffer + d'8' > xorwf FSR,W > btfss STATUS,Z > goto GIDLoop > return -- Best regards Tony mICros http://www.bubblesoftonline.com .....salesKILLspam.....bubblesoftonline.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Thanks for the reply Tony Up until now I've been using a single 1wire device and the ccs c compiler. I can read, write, get its address and do a crc on the data. Now, I want to talk to multiple devices. I have added 3 devices on the bus to experiment with. I want to read the serial number of each at power up and then individually address them. The problem is getting their serial numbers(addresses) I've read and re-read the dallas datasheet 187 '1 wire search algorithm', but can't get the code to work, I'm sure this is a hole in my understanding not in the dallas example code, but I can't help thinking theres a 'neater' ie shorter, quicker way of doing it. Regards Steve Tony Nixon wrote: {Quote hidden}> Tony Nixon wrote: > > I forgot to mention that this will only work for 1 device on the bus at > a time. There is a much more complicated procedure to use if multiple > devices are on the bus and need identification, but I haven't used that > method yet. > > > This is in assembler, but perhaps you can port it to C without much > > bother. > > > > Data in buffer after execution = 8 bytes > > > > Family Code - 1 byte > > ID Number - 6 bytes > > CRC - 1 Byte > > > > movlw Buffer ; set buffer pointer > > movwf FSR > > call INITDS ; start new transaction > > Send_Out Read_ROM ; read ROM command > > GIDLoop call IN_BYTE ; read bytes > > movwf INDF > > incf FSR > > movlw Buffer + d'8' > > xorwf FSR,W > > btfss STATUS,Z > > goto GIDLoop > > return > > -- > Best regards > > Tony > > mICros > http://www.bubblesoftonline.com > salesspam_OUTbubblesoftonline.com > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email @spam@listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com hint: To leave the PICList KILLspampiclist-unsubscribe-requestKILLspammitvma.mit.edu

One way that I handle this problem with some of my homebrew 1 wire devices is to have a simple protocol that allows me to send out an "are you there" code followed by an address. If a device with that address is on the bus, then it responds. The master runs through all possible addresses and takes note of the valid responses. By the way, it is useful in such a case to keep the "identity number or address" as simple as possible. I begin with address 1 and go 2, 3, 4. If I have designed the system to only have 5 slaves, I only have to test for 1, 2, 3, 4, 5. (I use 0 as a special address that means ALL slave devices. Useful for when I send a command like "reset all slaves") If the number of slaves is 8 or less, then I use an 8 bit register to keep track of active slaves. Each bit position represents one of the slaves. Fr. Thomas McGahee {Original Message removed}

Hello, If this is a one-of-a-kind product, you could just attach each device to the bus one at a time, get its address, and then write it down. You can now hardcode the three address into your program and don't have to worry about dynamically determining who is on the bus and what there serial numbers are. This solution is ideal, IMHO, for a one-of-a-kind project where devices will not be dynamically added/removed from the bus. Donovan Parks {Quote hidden}> Thanks for the reply Tony > > Up until now I've been using a single 1wire device and the ccs c > compiler. > I can read, write, get its address and do a crc on the data. > > Now, I want to talk to multiple devices. I have added 3 devices on the > bus to experiment with. I want to read the serial number of each at > power > up and then individually address them. The problem is getting their > serial > numbers(addresses) > > I've read and re-read the dallas datasheet 187 '1 wire search > algorithm', > but can't get the code to work, I'm sure this is a hole in my > understanding > not in the dallas example code, but I can't help thinking theres a > 'neater' > ie shorter, quicker way of doing it. > > Regards > > Steve > > Tony Nixon wrote: > > > Tony Nixon wrote: > > > > I forgot to mention that this will only work for 1 device on the bus > at > > a time. There is a much more complicated procedure to use if multiple > > devices are on the bus and need identification, but I haven't used > that > > method yet. > > > > > This is in assembler, but perhaps you can port it to C without much > > > bother. > > > > > > Data in buffer after execution = 8 bytes > > > > > > Family Code - 1 byte > > > ID Number - 6 bytes > > > CRC - 1 Byte > > > > > > movlw Buffer ; set buffer pointer > > > movwf FSR > > > call INITDS ; start new transaction > > > Send_Out Read_ROM ; read ROM command > > > GIDLoop call IN_BYTE ; read bytes > > > movwf INDF > > > incf FSR > > > movlw Buffer + d'8' > > > xorwf FSR,W > > > btfss STATUS,Z > > > goto GIDLoop > > > return > > > > -- > > Best regards > > > > Tony > > > > mICros > > http://www.bubblesoftonline.com > > RemoveMEsalesTakeThisOuTbubblesoftonline.com > > > > -- > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > email spamBeGonelistservspamBeGonemitvma.mit.edu with SET PICList DIGEST in the body > > -- > http://www.piclist.com hint: To leave the PICList > TakeThisOuTpiclist-unsubscribe-requestEraseMEspam_OUTmitvma.mit.edu > > -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

Donovan Parks wrote: > > Hello, > > If this is a one-of-a-kind product, you could just attach each device to the > bus one at a time, get its address, and then write it down. You can now > hardcode the three address into your program and don't have to worry about > dynamically determining who is on the bus and what there serial numbers are. > This solution is ideal, IMHO, for a one-of-a-kind project where devices will > not be dynamically added/removed from the bus. That is what I did for my system. A single sensor is connected and the host PC software enables the ID to be read and then stored in a small data base in the PICs EEPROM. -- Best regards Tony mICros http://www.bubblesoftonline.com salesEraseME.....bubblesoftonline.com -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestmitvma.mit.edu

Thomas McGahee wrote: > > One way that I handle this problem with some of my homebrew > 1 wire devices is to have a simple protocol that allows me > to send out an "are you there" code followed by an address. > If a device with that address is on the bus, then it responds. The trouble with the DS18S20 is that there is a 48 bit ID which would take some time to sift through on a random basis. -- Best regards Tony mICros http://www.bubblesoftonline.com RemoveMEsalesEraseMEEraseMEbubblesoftonline.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservspam_OUTKILLspammitvma.mit.edu with SET PICList DIGEST in the body