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Hello I am currently looking at using a LPC2106 in an access control unit to interface to a number of Dallas DS1990 iButtons. Am I correct in thinking that with a little code the iButtons could be interfaced to any of the LPC2106's GPIO pins ? Or would the iButton need to be interfaced to one the processors serial IO pins ? Thanks Ian |
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Interfacing a LPC2106 to a Dallas DS1990 iButton
Started by ●September 7, 2004
Reply by ●September 7, 20042004-09-07
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----- Original Message ----- From: "Ian Wraith" <> To: <> Sent: Tuesday, September 07, 2004 11:51 AM Subject: [lpc2000] Interfacing a LPC2106 to a Dallas DS1990 iButton > Hello > I am currently looking at using a LPC2106 in an access control > unit to interface to a number of Dallas DS1990 iButtons. Am I correct > in thinking that with a little code the iButtons could be interfaced > to any of the LPC2106's GPIO pins ? Or would the iButton need to be > interfaced to one the processors serial IO pins ? The interface has to be 'bit-banged' in software so any I/O chip may be used. Several people have done this sort of thing with PICs and AVRs, it shouldn't be difficult to modify the code for the LPC2106. Leon |
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Reply by ●September 7, 20042004-09-07
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Hello >The interface has to be 'bit-banged' in software so any I/O chip >may be used. Several people have done this sort of thing with PICs >and AVRs, it shouldn't be difficult to modify the code for the >LPC2106. Thanks Leon - I have used 8751's for this task before but this application looks a bit more demanding. Anyway I want to play with the LPC2xxx family :) Regards Ian |
Reply by ●September 7, 20042004-09-07
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At 11:51 AM 9/7/04 +0100, you wrote: >Hello > I am currently looking at using a LPC2106 in an access control >unit to interface to a number of Dallas DS1990 iButtons. Am I correct >in thinking that with a little code the iButtons could be interfaced >to any of the LPC2106's GPIO pins ? Or would the iButton need to be >interfaced to one the processors serial IO pins ? I've ported the Dallas 1-wire library using the 2106 timers. See http://www.aeolusdevelopment.com/Articles/download.html I need to do a little maintenance on it to bring it into line with the latest version of the newlib-lpc timing (it uses the previous version) but that's minor calling differences. Robert " 'Freedom' has no meaning of itself. There are always restrictions, be they legal, genetic, or physical. If you don't believe me, try to chew a radio signal. " Kelvin Throop, III |
Reply by ●September 7, 20042004-09-07
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On Sep 7, 2004, at 4:29 AM, Leon Heller wrote: >> I am currently looking at using a LPC2106 in an access control >> unit to interface to a number of Dallas DS1990 iButtons. Am I correct >> in thinking that with a little code the iButtons could be interfaced >> to any of the LPC2106's GPIO pins ? Or would the iButton need to be >> interfaced to one the processors serial IO pins ? > > The interface has to be 'bit-banged' in software so any I/O chip may be > used. Several people have done this sort of thing with PICs and AVRs, > it > shouldn't be difficult to modify the code for the LPC2106. > This maxim tech note talks about how to interface a one-wire device to a uart. Rather expensive use of resources, but if you're not using the uart for anything else... http://www.maxim-ic.com/appnotes.cfm/appnote_number/1189 Shannon |
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Reply by ●September 7, 20042004-09-07
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On 7 Sep 2004 at 11:51, Ian Wraith wrote: > Hello > I am currently looking at using a LPC2106 in an access control > unit to interface to a number of Dallas DS1990 iButtons. Am I correct > in thinking that with a little code the iButtons could be interfaced > to any of the LPC2106's GPIO pins ? Or would the iButton need to be > interfaced to one the processors serial IO pins ? > From a Maxim App-Note: 1-Wire devices operate in an open-drain environment on bus voltages ranging from 2.0V to 5.5V. Exact logic levels and minimum pullup voltages are device dependent, though generally parasite-power devices require minimum pullup voltage of 2.8V to recharge an internal storage capacitor used to supply power during periods when the data line is low. A 4.7k resistor typically serves as the pullup on the 1-Wire data line. The resistor provides logic-high signals passively, with the bus master and all slave devices driving the logic-low signals. Only the pins for the I2C interface are open drain, hence you probably will need to add a transistor or tri-state buffer type circuit as described in the Dallas/Maxim app notes. Regards Anton Erasmus-- A J Erasmus |
Reply by ●September 8, 20042004-09-08
