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joonho
Joined: 17 Oct 2012
Posts: 3
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| CVD code references |
 Posted: Wed Oct 17, 2012 9:34 pm |
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I'm trying to work on CVD code...has anyone have on it? If you have any code or circuit examples, I would love to see them.
Also, is it possible to control "C hold" with CCS-C function? If there is, what would it be?
Last, I bought DM183026-2 KIT from Microchip. Is there any example of CCS-C code that is used for this Kit? The manual of the kit only provides Hitech-C codes.
Thank you!! |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19540
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| Posted: Thu Oct 18, 2012 1:33 am |
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There is nothing 'rocket science' about this. Every function needed, is standard code.
Sequence involved is:
| Code: |
set_adc_channel(CH_FOR_Vdd); //depends on the PIC
delay_us(DATA1);
output_low(SENSE_PIN); //according to what pin you are using
output_float(SENSE_PIN);
set_adc_channel(CH_FOR_SENSE); //adc channel number for the pin
delay_cycles(GUESS); //This has to be tweaked to get it to work
val=read_adc();
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Now, some PIC's have Vdd available on the ADC multiplexer internally, while on others, another dummy pin needs to be used for this.
Also you need to be using the 10bit ADC mode, and an int16 for 'val' to get any reasonable resolution.
You need to delay long enough after selecting 'Vdd', for the internal hold capacitor to charge to Vdd, depends on the internal resistances of the chip - in the data sheet - and before the reading, another delay is needed, to allow Chold time to charge to the external signal.
The delay needed here, again depends on the PIC chosen. Keep as short as possible (go slightly below the recommended minimum, just reduces accuracy of the sampling, but improves response in this case).
Chold is _hardware_ it is the internal hold capacitor for the ADC. Nothing can change it, except choosing different chips. Later PIC's tend to have smaller values for this, allowing faster charging.
'Read the data sheet'.
Best Wishes |
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unisaco
Joined: 03 Dec 2012
Posts: 6
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| Posted: Sun Dec 30, 2012 10:04 pm |
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| Ttelmah wrote: | There is nothing 'rocket science' about this. Every function needed, is standard code.
Sequence involved is:
| Code: |
set_adc_channel(CH_FOR_Vdd); //depends on the PIC
delay_us(DATA1);
output_low(SENSE_PIN); //according to what pin you are using
output_float(SENSE_PIN);
set_adc_channel(CH_FOR_SENSE); //adc channel number for the pin
delay_cycles(GUESS); //This has to be tweaked to get it to work
val=read_adc();
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Now, some PIC's have Vdd available on the ADC multiplexer internally, while on others, another dummy pin needs to be used for this.
Also you need to be using the 10bit ADC mode, and an int16 for 'val' to get any reasonable resolution.
You need to delay long enough after selecting 'Vdd', for the internal hold capacitor to charge to Vdd, depends on the internal resistances of the chip - in the data sheet - and before the reading, another delay is needed, to allow Chold time to charge to the external signal.
The delay needed here, again depends on the PIC chosen. Keep as short as possible (go slightly below the recommended minimum, just reduces accuracy of the sampling, but improves response in this case).
Chold is _hardware_ it is the internal hold capacitor for the ADC. Nothing can change it, except choosing different chips. Later PIC's tend to have smaller values for this, allowing faster charging.
'Read the data sheet'.
Best Wishes
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Sorry for my noodle, but can you show me the full of this code ?
In my mind, for this code, we compare val value with some constant ?, for ex:
| Code: |
val=read_adc();
if (val > 200)
{
output_high(...)
} else {
output_low(...)
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Now I need to help that how can I make just only 1 LED blink within 1 mtouch button.
Thanks for your guidelines very much. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19540
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| Posted: Mon Dec 31, 2012 2:23 am |
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The starting point is the Microchip application note.
No, you'd probably not want to use a constant. You'd need to have some 'setup' code, and perform a reading without the button touched, and then again with it touched, and then calculate a value perhaps half way between these results, and use this as your 'detection' point. The capacitance _will_ change too much with the weather, and drift in the other components, for a constant to reliably be used.
Best Wishes |
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unisaco
Joined: 03 Dec 2012
Posts: 6
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| Posted: Mon Dec 31, 2012 11:01 am |
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| Ttelmah wrote: | The starting point is the Microchip application note.
No, you'd probably not want to use a constant. You'd need to have some 'setup' code, and perform a reading without the button touched, and then again with it touched, and then calculate a value perhaps half way between these results, and use this as your 'detection' point. The capacitance _will_ change too much with the weather, and drift in the other components, for a constant to reliably be used.
Best Wishes |
Sorry, but have you done this code ? and is it running as well ?
Based on this code, I can make my application run (toggle LED each time touch), but when I touch to any A/DC input not yet be used in 16F887, it also effective (toggle LED) => maybe it's noise.
My hardware is using PIC 16F887, AN0 => touch button, AN1 => VCC to discharge c_hold.
Now I'm very confuse, waste many time to do this project.
P/S: I use PICKIT 2 to program code and also use power get from PICKIT2 to run my circuit => is there any noise ? |
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Mike Walne
Joined: 19 Feb 2004
Posts: 1785
Location: Boston Spa UK
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| Posted: Mon Dec 31, 2012 12:13 pm |
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| Quote: | Based on this code, I can make my application run (toggle LED each time touch), but when I touch to any A/DC input not yet be used in 16F887, it also effective (toggle LED) => maybe it's noise.
My hardware is using PIC 16F887, AN0 => touch button, AN1 => VCC to discharge c_hold.
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Time to get the 'scope out and investigate.
What's connected to the other ADC pins, or are they all floating?
Mike |
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