From: yup <yup...@ho...> - 2008-12-17 20:51:59
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I am trying to test the GPIO on gumstix via break-out expension board. I set GPIO #43 pin as OUT and GPIO #45 as IN. Do I need something else to let the output of GPIO 43 to turn on/off a LED light because I used a switch statement to keep sending 1 to GPIO 43 but the light is not on. I read the value from PIN 45 and it seems it is always value 1. How can I let gumstix read a 0 from the outside device, like a switch? Thanks a lot, Lee -- View this message in context: http://www.nabble.com/Very-basic-GPIO-questions-tp21060854p21060854.html Sent from the Gumstix mailing list archive at Nabble.com. |
From: Oliver D. <o.d...@gm...> - 2008-12-17 22:38:45
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yup wrote: > I am trying to test the GPIO on gumstix via break-out expension board. I set > GPIO #43 pin as OUT and GPIO #45 as IN. > Do I need something else to let the output of GPIO 43 to turn on/off a LED > light because I used a switch statement to keep sending 1 to GPIO 43 but the > light is not on. > > I read the value from PIN 45 and it seems it is always value 1. How can I > let gumstix read a 0 from the outside device, like a switch? > http://www.micahcarrick.com/files/atmega8/tutorial_3/pullup.png > Thanks a lot, > > Lee > |
From: yup <yup...@ho...> - 2008-12-18 14:53:07
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Thank you Oliver and Dave, Can I use the VCC and GND on the Gumstix board? Thanks, Lee -- View this message in context: http://www.nabble.com/Very-basic-GPIO-questions-tp21060854p21074281.html Sent from the Gumstix mailing list archive at Nabble.com. |
From: Oliver D. <o.d...@gm...> - 2008-12-18 15:24:01
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yup wrote: > Thank you Oliver and Dave, Can I use the VCC and GND on the Gumstix board? > > Yes! > Thanks, > > Lee > |
From: yup <yup...@ho...> - 2008-12-20 02:33:09
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oliver, thank you for you last reply. I made the input work! Now, do you have some hints of the GPIO output for me? I do not think the voltage between a GPIO pin and GND is enough for me to power on a motor. How can I connect the wire to control the motor via GPIO? I read this link http://pubs.gumstix.org/documents/Powering_a_Gumstix.pdf Two points unkown to me, In Figure 2, What is the 1 position for S1? What kind of resister, e.g. R4 R3 should I use? Thanks a lot, Lee -- View this message in context: http://www.nabble.com/Very-basic-GPIO-questions-tp21060854p21101262.html Sent from the Gumstix mailing list archive at Nabble.com. |
From: Oliver D. <o.d...@gm...> - 2008-12-20 04:31:21
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Hi Lee, yup wrote:oliver, thank you for you last reply. I made the input work! Now, do you have > some hints of the GPIO output for me? I do not think the voltage between a > GPIO pin and GND is enough for me to power on a motor. How can I connect the > wire to control the motor via GPIO? I read this link > What kind of motor do you want to use (Volt / Ampere) ? One direction or 2 (left and right) ? > http://pubs.gumstix.org/documents/Powering_a_Gumstix.pdf > Two points unkown to me, > > In Figure 2, > What is the 1 position for S1? > Power-Off > What kind of resister, e.g. R4 R3 should I use? > Dont know (lower than 1 Ohm), i think, it is not good, if you use an resistor in the power lines. > Thanks a lot, > > Lee > Sorry, more later, i must sleep now ! Good Night Olli |
From: Oliver D. <o.d...@gm...> - 2008-12-20 13:13:35
Attachments:
gpio.png
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Dave Hylands wrote: > Hi Lee, > > >> oliver, thank you for you last reply. I made the input work! Now, do you have >> some hints of the GPIO output for me? I do not think the voltage between a >> GPIO pin and GND is enough for me to power on a motor. How can I connect the >> wire to control the motor via GPIO? >> > > You'll need a motor controller, sometimes also called an H-Bridge. > There are many different motor controllers, which mostly vary by the > amount of current that they're capable of delivering. So you need to > know what the maximum current your motor can draw, sometimes known as > the stall current, and then pick a motor controller which can drive > that much current. > > Here are some places you can get motor controllers: > <http://www.pololu.com/> > <http://www.lynxmotion.com/> > <http://www.acroname.com/> > > >> I read this link >> http://pubs.gumstix.org/documents/Powering_a_Gumstix.pdf >> >> Two points unkown to me, >> >> In Figure 2, >> What is the 1 position for S1? >> > > That's otherwise known as OFF. > > >> What kind of resister, e.g. R4 R3 should I use? >> > > All of the resistors mentioned in this document are just there to show > that the wire itself has resistance (see the first paragraph on page > 2). These resistances are determined by the size and length of the > wire. Even though there aren't explicit resistors, depending on the > amount of current, you can have some significant voltage variations > (so you need to be familiar with ohms law). > <http://en.wikipedia.org/wiki/Ohm's_law> > > some basic io's: LED-Output Switch-Input (internal Pullup-Resistor) Switch-Input (external Pullup-Resistor) Optokoppler-Output Transistor-Output (max 100mA / use Mosfet-Transistors for more Power) Driver-Array-Output (max 500mA / Line and max 2A over all) |
From: yup <yup...@ho...> - 2008-12-20 16:29:25
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Dave, I think the point is I do not understand how to let a GPIO play the role as a switch for output. For test only, i am going to setup a LED light(5V), so the LED need extra power supply, e.g. a 5V battery or connecting to USB port on gumstix. Now, the problem is, how can I turn on and off the LED by set particular GPIO 1 and 0 in program? Thanks again, Lee -- View this message in context: http://www.nabble.com/Very-basic-GPIO-questions-tp21060854p21106622.html Sent from the Gumstix mailing list archive at Nabble.com. |
From: Oliver D. <o.d...@gm...> - 2008-12-21 05:58:53
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yup wrote: > Dave, > > I think the point is I do not understand how to let a GPIO play the role as > a switch for output. For test only, i am going to setup a LED light(5V), so > the LED need extra power supply, e.g. a 5V battery or connecting to USB port > on gumstix. Now, the problem is, how can I turn on and off the LED by set > particular GPIO 1 and 0 in program? > > Thanks again, > > Lee > http://docwiki.gumstix.org/index.php/Tips_and_tricks#Access_GPIOs_from_user-space |
From: Dave H. <dhy...@gm...> - 2008-12-21 17:59:37
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Hi Lee, > I think the point is I do not understand how to let a GPIO play the role as > a switch for output. For test only, i am going to setup a LED light(5V), so > the LED need extra power supply, e.g. a 5V battery or connecting to USB port > on gumstix. Now, the problem is, how can I turn on and off the LED by set > particular GPIO 1 and 0 in program? LEDs generally don't need to use an external power supply. They can be run off the voltage provided by the gumstix. Setting a GPIO to 1 causes that pin to have a voltage (3.3v for the verdex). Setting a GPIO to 0 causes that pin to have a voltage of 0v. Lets say that GPIO 47 (just a random number I picked) is the one you want to use. You can connect a multimeter up between ground and that pin, and then you can do the following: modprobe proc_gpio echo "GPIO out set" > /proc/gpio/GPIO47 and you should measure 3.3v on gpio 47. If you do echo "GPIO out clear" > /proc/gpio/GPIO47 and you should get 0v. Now, for connecting to external supplies, you generally need to use a transistor or MOSFET to act as a switch. The GPIO pin can only source or sink a few milliamps of current. Here's an example of how to connect up "high current". For some circuits you may also need to translate he 3.3v voltage into a higher voltage in order to make the circuits work properly. -- Dave Hylands Shuswap, BC, Canada http://www.DaveHylands.com/ |
From: Dave H. <dhy...@gm...> - 2008-12-21 18:00:16
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Whoops - I forgot the link in the last post: > Here's an example of how to connect up "high current". For some > circuits you may also need to translate he 3.3v voltage into a higher > voltage in order to make the circuits work properly. <http://www.mcmanis.com/chuck/robotics/circuits/circuits.htm> -- Dave Hylands Shuswap, BC, Canada http://www.DaveHylands.com/ |
From: yup <yup...@ho...> - 2008-12-21 18:09:53
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I got you, "MOSFET to act as a switch" is what i need to study. I will read your url and try to make it. Thanks a lot, Lee Dave Hylands wrote: > > Hi Lee, > >> I think the point is I do not understand how to let a GPIO play the role >> as >> a switch for output. For test only, i am going to setup a LED light(5V), >> so >> the LED need extra power supply, e.g. a 5V battery or connecting to USB >> port >> on gumstix. Now, the problem is, how can I turn on and off the LED by set >> particular GPIO 1 and 0 in program? > > LEDs generally don't need to use an external power supply. They can be > run off the voltage provided by the gumstix. > > Setting a GPIO to 1 causes that pin to have a voltage (3.3v for the > verdex). Setting a GPIO to 0 causes that pin to have a voltage of 0v. > > Lets say that GPIO 47 (just a random number I picked) is the one you > want to use. You can connect a multimeter up between ground and that > pin, and then you can do the following: > > modprobe proc_gpio > > echo "GPIO out set" > /proc/gpio/GPIO47 > > and you should measure 3.3v on gpio 47. If you do > > echo "GPIO out clear" > /proc/gpio/GPIO47 > > and you should get 0v. > > Now, for connecting to external supplies, you generally need to use a > transistor or MOSFET to act as a switch. The GPIO pin can only source > or sink a few milliamps of current. > > Here's an example of how to connect up "high current". For some > circuits you may also need to translate he 3.3v voltage into a higher > voltage in order to make the circuits work properly. > > -- > Dave Hylands > Shuswap, BC, Canada > http://www.DaveHylands.com/ > > ------------------------------------------------------------------------------ > _______________________________________________ > gumstix-users mailing list > gum...@li... > https://lists.sourceforge.net/lists/listinfo/gumstix-users > > -- View this message in context: http://www.nabble.com/Very-basic-GPIO-questions-tp21060854p21117508.html Sent from the Gumstix mailing list archive at Nabble.com. |
From: Dave H. <dhy...@gm...> - 2008-12-17 22:40:24
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Hi Lee, > I am trying to test the GPIO on gumstix via break-out expension board. I set > GPIO #43 pin as OUT and GPIO #45 as IN. > Do I need something else to let the output of GPIO 43 to turn on/off a LED > light because I used a switch statement to keep sending 1 to GPIO 43 but the > light is not on. How do you have the light wired up? Are you sure you didn't connect the LED in backwards? LEDs only work in one direction. Where exactly did you connect the LED to? Did you use a current limiting resistor? > I read the value from PIN 45 and it seems it is always value 1. How can I > let gumstix read a 0 from the outside device, like a switch? How did you wire up the switch? -- Dave Hylands Shuswap, BC, Canada http://www.DaveHylands.com/ |
From: Dave H. <dhy...@gm...> - 2008-12-20 04:48:49
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Hi Lee, > oliver, thank you for you last reply. I made the input work! Now, do you have > some hints of the GPIO output for me? I do not think the voltage between a > GPIO pin and GND is enough for me to power on a motor. How can I connect the > wire to control the motor via GPIO? You'll need a motor controller, sometimes also called an H-Bridge. There are many different motor controllers, which mostly vary by the amount of current that they're capable of delivering. So you need to know what the maximum current your motor can draw, sometimes known as the stall current, and then pick a motor controller which can drive that much current. Here are some places you can get motor controllers: <http://www.pololu.com/> <http://www.lynxmotion.com/> <http://www.acroname.com/> > I read this link > http://pubs.gumstix.org/documents/Powering_a_Gumstix.pdf > > Two points unkown to me, > > In Figure 2, > What is the 1 position for S1? That's otherwise known as OFF. > What kind of resister, e.g. R4 R3 should I use? All of the resistors mentioned in this document are just there to show that the wire itself has resistance (see the first paragraph on page 2). These resistances are determined by the size and length of the wire. Even though there aren't explicit resistors, depending on the amount of current, you can have some significant voltage variations (so you need to be familiar with ohms law). <http://en.wikipedia.org/wiki/Ohm's_law> -- Dave Hylands Shuswap, BC, Canada http://www.DaveHylands.com/ |