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by pygmy_giant
Mon Jul 23, 2012 9:24 pm
Forum: Automation, sensing and robotics
Topic: Does the GPIO have schmitt trigger inputs ?
Replies: 1
Views: 1993

Re: Does the GPIO have schmitt trigger inputs ?

Ignore me - the gertboard uses 74xx244 so I guess I should too...
by pygmy_giant
Mon Jul 23, 2012 7:18 pm
Forum: Automation, sensing and robotics
Topic: Does the GPIO have schmitt trigger inputs ?
Replies: 1
Views: 1993

Does the GPIO have schmitt trigger inputs ?

Hi I'm designing a sensor and want to simplify the design as much as possible. At present the output is a falling voltage level which is 'tidied up' via a schmitt trigger to give a nice square edged pulse. It has just occured to me that this might not be necessary if the Pi's GPIO already have schmi...
by pygmy_giant
Mon Jul 23, 2012 5:50 pm
Forum: Bare metal, Assembly language
Topic: Programming in Basic on Bare Metal Tutorial 1
Replies: 50
Views: 21055

Re: Programming in Basic on Bare Metal Tutorial 1

'for fill it' - thats a joke right? (cf speil chucker)

My spelling and grammar may be bad, but my assembler is non-existent, so you'll also have to stupid-proof the tutorials for HL noobs like me...
by pygmy_giant
Mon Jul 23, 2012 4:38 pm
Forum: Automation, sensing and robotics
Topic: theramin
Replies: 59
Views: 14102

Re: theramin

If I use an R of 5M and C of 22pF in the 555 monostable circuit then the zero reading pulse length before magnification would be 1.1RC = 1.1 x 5e6 x 22e-12 = 121e-6 s If I attempt to match the theraminvision sensitivity of 0.00028pF, then this unmagnified pulse value with minimum modified capacitanc...
by pygmy_giant
Mon Jul 23, 2012 12:51 am
Forum: Automation, sensing and robotics
Topic: theramin
Replies: 59
Views: 14102

Re: theramin

Should look like this: http://www.nsd.uk.com/miscellaneous/extenderII.PNG those values make for reasonable linear ratios if a 5M resistor is used in the pulse generating monostable circuit: http://www.nsd.uk.com/miscellaneous/charge_curveII.PNG need to tweek these values and calculate some scenarios...
by pygmy_giant
Mon Jul 23, 2012 12:07 am
Forum: Automation, sensing and robotics
Topic: theramin
Replies: 59
Views: 14102

Re: theramin

not unless I put another resistor in series with the capacitor in the pulse extendor circuit to prevent the capacitor from completely charging before the pulse from the monostable input has finished
by pygmy_giant
Sat Jul 21, 2012 10:51 pm
Forum: Off topic discussion
Topic: Which Oscilloscope?
Replies: 41
Views: 13607

Re: Which Oscilloscope?

I know nothing about oscilloscopes, but like the look of this one: http://www.velleman.eu/products/view/?id=384636
by pygmy_giant
Sat Jul 21, 2012 10:34 pm
Forum: For sale
Topic: Pibow (a colourful case for your Raspberry Pi)
Replies: 122
Views: 34680

Re: Pibow (a colourful case for your Raspberry Pi)

4 short female pcb stand-offs might mate 2 together....?
by pygmy_giant
Sat Jul 21, 2012 6:55 pm
Forum: Other projects
Topic: case idea feedback
Replies: 10
Views: 2123

Re: case idea feedback

rugged-I like it!
by pygmy_giant
Sat Jul 21, 2012 6:23 pm
Forum: Bare metal, Assembly language
Topic: Programming in Basic on Bare Metal Tutorial 1
Replies: 50
Views: 21055

Re: Programming in Basic on Bare Metal Tutorial 1

Nice site - I found the instructions easy to follow, and it did what it said on the tin! Looking forward to tutorial 2...
by pygmy_giant
Sat Jul 21, 2012 5:00 pm
Forum: C/C++
Topic: GPIO Programming and Interrupts
Replies: 64
Views: 33719

Re: GPIO Programming and Interrupts

looking at how that would work with dexos (kernel compiled via fasarm) - not sure I need linux... but would like I2C and am not sure how to write my own driver so maybe I do - but then again maybe writing an I2C driver using fbasic would not be that hard?
by pygmy_giant
Fri Jul 20, 2012 10:38 pm
Forum: Automation, sensing and robotics
Topic: theramin
Replies: 59
Views: 14102

Re: theramin

You're right. What I should have said is 'the length of the pulse unmodified by the arial, once it has been multiplied' - in other words, what the reading would be if nothing external is effecting the capacitance of the circuit via the arial. so basicly you're taking the length of the pulse which ha...
by pygmy_giant
Fri Jul 20, 2012 10:29 pm
Forum: C/C++
Topic: GPIO Programming and Interrupts
Replies: 64
Views: 33719

Re: GPIO Programming and Interrupts

sorry to 'interrupt' but when I think of 'GPIO' + 'interrupt' in the same sentace I think of pages 25 -30 and 79 most of all 109 onwards in the Boardcom BCM2835 ARM Peripherals datasheet - is that what was intended by the OP? I'm more interested by the way that interrupts work on a hardware level th...
by pygmy_giant
Fri Jul 20, 2012 12:20 am
Forum: Automation, sensing and robotics
Topic: Laundry Notifications
Replies: 8
Views: 4242

Re: Laundry Notifications

or you could just used the 2nd and 3rd ones with switched output
by pygmy_giant
Fri Jul 20, 2012 12:05 am
Forum: Automation, sensing and robotics
Topic: Laundry Notifications
Replies: 8
Views: 4242

Re: Laundry Notifications

http://www.ebay.co.uk/itm/Sound-Sensor-Module-for-Arduino-Sensor-Shield-PIC-MCU-/200783452322?pt=UK_Sound_Vision_Other&hash=item2ebfa058a2 ? think it could be used with th GPIO if added to some extra circuitry to make a switched output - there are also other similar modules on the market that are ju...
by pygmy_giant
Thu Jul 19, 2012 11:47 pm
Forum: Automation, sensing and robotics
Topic: theramin
Replies: 59
Views: 14102

Re: theramin

Thanks for the permission to try something different. No "permission", :shock: I rather meant it as encouragement to try something new, I'm not your teacher or something like that, so who am I to give you "permission". Learning by doing (failing and trying again) is the best way to gain insight. :m...
by pygmy_giant
Thu Jul 19, 2012 11:05 pm
Forum: C/C++
Topic: GPIO Programming and Interrupts
Replies: 64
Views: 33719

Re: GPIO Programming and Interrupts

ah - I see - thanks.
by pygmy_giant
Thu Jul 19, 2012 10:03 pm
Forum: C/C++
Topic: GPIO Programming and Interrupts
Replies: 64
Views: 33719

Re: GPIO Programming and Interrupts

That would be much appreciated!

I am intending on using linux as only an intermediate solution before hopefully going bare metal....
by pygmy_giant
Thu Jul 19, 2012 9:42 pm
Forum: C/C++
Topic: GPIO Programming and Interrupts
Replies: 64
Views: 33719

Re: GPIO Programming and Interrupts

I cant see how that's possible without an overseeing program to allocate prioraties that's running all the time?

What am I missing?

Is it to do with the Pi having a CPU and a GPU ?

Surely otherwise if it has one processor it can only truely do one thing at a time...?
by pygmy_giant
Thu Jul 19, 2012 9:21 pm
Forum: Python
Topic: What's the difference between "=" and "=="?
Replies: 18
Views: 3600

Re: What's the difference between "=" and "=="?

in php you can have '==='.

The additional '=' means 'has same variable type' as integers can otherwise be deemed equivelent to a string resembling that integer.
by pygmy_giant
Thu Jul 19, 2012 8:43 pm
Forum: Automation, sensing and robotics
Topic: theramin
Replies: 59
Views: 14102

Re: theramin

Actually, the more I think about this problem, the more I think: 'oscilator schmoscilator'. My previus monostable solution 'worked' as the width of the pulse by definition is related to the capacitance as modified by the arial, the only trouble with it was that the variaion in capacitance was tiny a...
by pygmy_giant
Thu Jul 19, 2012 6:42 pm
Forum: Advanced users
Topic: Cooling Ram + CPU
Replies: 108
Views: 54509

Re: Cooling Ram + CPU

No one's mentioned the peltier effect - you could construct the case out of 6 large peltier pannels powered from the pi's GPIO and then stick on comoposite copper/ally fins with a fan attached and fill it with mineral oil - job done.
by pygmy_giant
Thu Jul 19, 2012 6:15 pm
Forum: C/C++
Topic: GPIO Programming and Interrupts
Replies: 64
Views: 33719

Re: GPIO Programming and Interrupts

I'm interested in interrupts but might settle for polling. My balancing robot will need to check its posture about every 7ms so the question for me is: Should I have one big infinite loop which gathers info from all the sensors and then makes decisions based upon that data, or can I have interupt dr...
by pygmy_giant
Thu Jul 19, 2012 5:54 pm
Forum: Automation, sensing and robotics
Topic: Relay control with gpio
Replies: 11
Views: 4012

Re: Relay control with gpio

If you're dippy like me you might have connected it to the wrong very small non-desript one of many and hard to see GPIO pins.

If you've got a multi meter you could test the GPIO pins to see if their switching as intended,
by pygmy_giant
Thu Jul 19, 2012 5:26 pm
Forum: Automation, sensing and robotics
Topic: Balancing Robot
Replies: 183
Views: 54235

Re: Balancing Robot

My motors arrived in the post this morning: http://www.nsd.uk.com/miscellaneous/motors.png The body is 25mm x 50mm and they run at 6v. They have a planetary gear box that gears down to 300rpm. Lots of torque - I hope they're fast enough! They will be powered via an I2C controlled pwm hbridge which i...

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