From: <tim...@co...> - 2007-01-17 23:09:24
|
Hi Dave, Brian, Would it be possible to have a switch connected to ground via a resistor, than program the gpio as output, program it high then enable the edge detect interrupt to detect a falling edge? Tim -------------- Original message ---------------------- From: "Dave Hylands" <dhy...@gm...> > Hi Brian, > > > I am finally a the point where I want to use my switch. I have the switch tied > > to GPIO84. When the button is pressed, The signal (4V) should go high but I > > see nothing. I am using the gpio-event monitor and have it set to 84:b:0 so I > > should see the signal on either the rising or falling edge. The one thing we > > are thinking is that I need a resistor tied to ground for a strong reference > > ground. The signal is a 4V high, which I think should be adequate. Any one > > have any thoughts as to why I cant see the button presses? > > The conventional way to set this up is to have the pushbottom go > between ground and the input, and have a pullup resistor go between > 3.3v and the input. > > Or you can flip it around and have the button go between 3.3v and the > input and have a pull-down resistor go between the input and ground. > > The resistor value should be at least 10k. 20K or 47K should also work fine. > > Using a raw button, you'll probably need to use 84:b:20 or else you'll > get several button press events each time you press or release the > button. > > GPIO84 would be the NSSP MISO line. > > -- > Dave Hylands > Vancouver, BC, Canada > http://www.DaveHylands.com/ > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys - and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users |
From: <tim...@co...> - 2007-01-18 00:03:26
|
Hi Dave, Yes, I agree, KISS. Funny thing is I was just revieving our customer schematics and they used a switch connected to a resistor to ground without pull up. I tried to tell them it would not work, but they blew me off suggesting software people should not be looking at schematics. ;-) Tim BTW: Since this question has been asked more than once on this forum, maybe we sould do a wiki page? -------------- Original message ---------------------- From: "Dave Hylands" <dhy...@gm...> > Hi Tim, > > > Would it be possible to have a switch connected to ground > > via a resistor, than program the gpio as output, program it > > high then enable the edge detect interrupt to detect a falling > > edge? > > Programming the edge detect interrupt requires that it be configured > as an input. You really don't ever want to run the risk of having the > pin configured as an output when the input might be connected to a > different voltage (say the switch is closed). > > Since you'd need a resistor anyways, why not just connect it up in the > conventional manner? > > Here are the two conventional ways of connecting a switch. > > 3.3v ---\/\/\/\/-----+-----o/ o----- Gnd > > GND ---\/\/\/\/-----+-----o/ o----- 3.3v > > Where the + goes to the input. > > -- > Dave Hylands > Vancouver, BC, Canada > http://www.DaveHylands.com/ > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys - and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users |
From: Dave H. <dhy...@gm...> - 2007-01-18 00:13:10
|
Hi Tim, > Yes, I agree, KISS. Funny thing is I was just revieving > our customer schematics and they used a switch > connected to a resistor to ground without pull up. > I tried to tell them it would not work, but they blew > me off suggesting software people should not be > looking at schematics. ;-) > > BTW: Since this question has been asked more than > once on this forum, maybe we sould do a wiki page? I'll create some schematics and post them on the GPIO Event page, and give an explanation as to why they need to be wired the way they are. With some processors, like the ATMega128 on the robostix, there are builtin pullup resistors which can be enabled. The pxa255 doesn't have these though, so this is why an external one is needed. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |
From: Dave H. <dhy...@gm...> - 2007-01-18 00:35:44
|
Hi Tim, > Yes, I agree, KISS. Funny thing is I was just revieving > our customer schematics and they used a switch > connected to a resistor to ground without pull up. > I tried to tell them it would not work, but they blew > me off suggesting software people should not be > looking at schematics. ;-) > > BTW: Since this question has been asked more than > once on this forum, maybe we sould do a wiki page? I'll create some schematics and post them on the GPIO Event page, and give an explanation as to why they need to be wired the way they are. With some processors, like the ATMega128 on the robostix, there are builtin pullup resistors which can be enabled. The pxa255 doesn't have these though, so this is why an external one is needed. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |
From: Brian W. <bw...@ir...> - 2007-01-18 13:55:05
|
On Wednesday 17 January 2007 19:03, tim...@co... wrote: > Hi Dave, > > Yes, I agree, KISS. Funny thing is I was just revieving > our customer schematics and they used a switch > connected to a resistor to ground without pull up. > I tried to tell them it would not work, but they blew > me off suggesting software people should not be > looking at schematics. ;-) > Funny, when the tech I have adding the button on asked about the resistor to ground initially and button setup I just said don't worry. Maybe SW people ought not be doing EE work :) > > Tim > > BTW: Since this question has been asked more than > once on this forum, maybe we sould do a wiki page? > > -------------- Original message ---------------------- > From: "Dave Hylands" <dhy...@gm...> > > > Hi Tim, > > > > > Would it be possible to have a switch connected to ground > > > via a resistor, than program the gpio as output, program it > > > high then enable the edge detect interrupt to detect a falling > > > edge? > > > > Programming the edge detect interrupt requires that it be configured > > as an input. You really don't ever want to run the risk of having the > > pin configured as an output when the input might be connected to a > > different voltage (say the switch is closed). > > > > Since you'd need a resistor anyways, why not just connect it up in the > > conventional manner? > > > > Here are the two conventional ways of connecting a switch. > > > > 3.3v ---\/\/\/\/-----+-----o/ o----- Gnd > > > > GND ---\/\/\/\/-----+-----o/ o----- 3.3v > > > > Where the + goes to the input. > > > > -- > > Dave Hylands > > Vancouver, BC, Canada > > http://www.DaveHylands.com/ > > > > ------------------------------------------------------------------------- > > Take Surveys. Earn Cash. Influence the Future of IT > > Join SourceForge.net's Techsay panel and you'll get the chance to share > > your opinions on IT & business topics through brief surveys - and earn > > cash > > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > > _______________________________________________ > > gumstix-users mailing list > > gum...@li... > > https://lists.sourceforge.net/lists/listinfo/gumstix-users > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share > your opinions on IT & business topics through brief surveys - and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users |
From: Patrick D. <wp...@gm...> - 2007-01-25 16:21:27
|
On 1/17/07, Dave Hylands <dhy...@gm...> wrote: > Hi Tim, > > > Yes, I agree, KISS. Funny thing is I was just revieving > > our customer schematics and they used a switch > > connected to a resistor to ground without pull up. > > I tried to tell them it would not work, but they blew > > me off suggesting software people should not be > > looking at schematics. ;-) > > > > BTW: Since this question has been asked more than > > once on this forum, maybe we sould do a wiki page? > > I'll create some schematics and post them on the GPIO Event page, and > give an explanation as to why they need to be wired the way they are. > > With some processors, like the ATMega128 on the robostix, there are > builtin pullup resistors which can be enabled. The pxa255 doesn't have > these though, so this is why an external one is needed. > If I am reading the pinout for the 60 pin correctly, I don't see the 3.3V regulated rail anywhere on it. Do folks typically connect the pullup reisistor to V_BATT and rely on the ESD diodes (presumably) built into the PXA255 to limit the input voltage? Or do you typically add a 3.3V rail somewhere on a daughter card, which you use for the top of the pullup? I'm asking because I want to attach a push button to a breakout-gs board, and I don't have 3.3V running around anywhere else. What to folks typically do? --wpd |
From: Dave H. <dhy...@gm...> - 2007-01-25 17:51:58
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Hi Patrick, > If I am reading the pinout for the 60 pin correctly, I don't see the > 3.3V regulated rail anywhere on it. Do folks typically connect the > pullup reisistor to V_BATT and rely on the ESD diodes (presumably) > built into the PXA255 to limit the input voltage? Or do you typically > add a 3.3V rail somewhere on a daughter card, which you use for the > top of the pullup? Every daughtercard has its own voltage regulator. You should grab the 3.3v from there. You definitely shouldn't connect the resistor to V_BATT. > I'm asking because I want to attach a push button to a breakout-gs > board, and I don't have 3.3V running around anywhere else. The breakout-gs has a bunch of pins labelled VCC. Theses are all 3.3v -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |
From: Chris D. <chr...@gm...> - 2007-01-25 16:43:38
|
I grab 3.3v from one of the VCC pins on the breakout-gs. Chris On 1/25/07, Patrick Doyle <wp...@gm...> wrote: > On 1/17/07, Dave Hylands <dhy...@gm...> wrote: > > Hi Tim, > > > > > Yes, I agree, KISS. Funny thing is I was just revieving > > > our customer schematics and they used a switch > > > connected to a resistor to ground without pull up. > > > I tried to tell them it would not work, but they blew > > > me off suggesting software people should not be > > > looking at schematics. ;-) > > > > > > BTW: Since this question has been asked more than > > > once on this forum, maybe we sould do a wiki page? > > > > I'll create some schematics and post them on the GPIO Event page, and > > give an explanation as to why they need to be wired the way they are. > > > > With some processors, like the ATMega128 on the robostix, there are > > builtin pullup resistors which can be enabled. The pxa255 doesn't have > > these though, so this is why an external one is needed. > > > If I am reading the pinout for the 60 pin correctly, I don't see the > 3.3V regulated rail anywhere on it. Do folks typically connect the > pullup reisistor to V_BATT and rely on the ESD diodes (presumably) > built into the PXA255 to limit the input voltage? Or do you typically > add a 3.3V rail somewhere on a daughter card, which you use for the > top of the pullup? > > I'm asking because I want to attach a push button to a breakout-gs > board, and I don't have 3.3V running around anywhere else. > > What to folks typically do? > > --wpd > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys - and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users > |
From: Patrick D. <wp...@gm...> - 2007-01-25 17:54:38
|
On 1/25/07, Chris Dollar <chr...@gm...> wrote: > I grab 3.3v from one of the VCC pins on the breakout-gs. > > Chris > Ahhh... That falls in the category of "add a 3,3V rail somewhere on a daughter card". I missed the LDO in the manual :-) Thanks. --wpd |
From: EXT-McGhehey, M. J <Mar...@bo...> - 2007-01-25 18:06:19
|
=20 Many of the Gumstix expansion boards have components on them that are identified on the silk screen and schematics with an FBxx type of indication (i.e. FB31, FB34, FB32). What are these devices? Fuses? Varistors? Thanks Mark =20 |
From: Dave H. <dhy...@gm...> - 2007-01-25 18:13:51
|
Hi Mark, > Many of the Gumstix expansion boards have components on them that are > identified on the silk screen and schematics with an FBxx type of > indication (i.e. FB31, FB34, FB32). > > What are these devices? Fuses? Varistors? Ferrite Beads. These are like little inductors that help to filter out noise on the signal lines. If I remember correctly, they act like a low-impedance for DC or low frequencies and act like a high-impedance for high frequency signals (where the definition of high depends on the inductance of the bead). But my knowledge in this area is quite hazy (lots of hand-waving) so don't read too much into it. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |
From: Dave H. <dhy...@gm...> - 2007-01-17 23:28:09
|
Hi Tim, > Would it be possible to have a switch connected to ground > via a resistor, than program the gpio as output, program it > high then enable the edge detect interrupt to detect a falling > edge? Programming the edge detect interrupt requires that it be configured as an input. You really don't ever want to run the risk of having the pin configured as an output when the input might be connected to a different voltage (say the switch is closed). Since you'd need a resistor anyways, why not just connect it up in the conventional manner? Here are the two conventional ways of connecting a switch. 3.3v ---\/\/\/\/-----+-----o/ o----- Gnd GND ---\/\/\/\/-----+-----o/ o----- 3.3v Where the + goes to the input. -- Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ |