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A bit confused
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Date: 2006/04/02 03:46
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By: streddy
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Status: User
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Karma: 0
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| Posts: 7 |   |
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Hello,
I am new to using USB microcontrollers . I have just gone through the 'Basic USB' article and have found it to be quite helpful in my project.
However I am a bit confused about the difference between the PIC code and the Application code. My project involves taking the information from the PIC18F4550 A/D converter and passing it to the PC via USB for storage in any type of file.
Do I need to write my code using MPLAB/C18 or C#Sharp or both?
Thanks
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Re:A bit confused
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Date: 2006/04/02 10:48
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By: dariog
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Status: User
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Karma: 6
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| Posts: 107 | |
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Hi, you'll need both,
PIC code goes on the PIC  and performs the needed tasks to get A/D results, store them , and send them to the PC.
On the PC, you'll receive that data, in the format you specified on the PIC, via USB: and you'll need a VisualBasic, or C/C++/C# software to handle them (it's not as easy as opening a Serial Port).
Start out with an easy example!
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Re:A bit confused
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Date: 2006/04/02 21:56
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By: streddy
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Status: User
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Karma: 0
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| Posts: 7 | |
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Thanks for the response,
At this time I have set up code to get the data from the ADC into PORTB which is an I/O port that can be "software programmed for internal pull-ups" (according to the 4550 datasheet).
By editing the code provided in the this USB example article would I be able to read the contents of PORTB? For example, similar to the way that the Add button reads the sum of the two inputs on MCU - would I be able to set up a button that reads the contents of PORTB?
Is it not that simple?
Thank you,
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Re:A bit confused
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Date: 2006/04/03 12:47
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By: dariog
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Status: User
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Karma: 6
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| Posts: 107 | |
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sure, you can.
I haven't seen where exaclty , in the project, the PIC reads PORTB.
But you just have to setup ADC (which, incidentally, are usually on ports A and E), perform the conversion (OpenADC/SetChanADC/ConvertADC) and feed the result to the routine which talks to the USB.
You may create a packet which contains more than just one converted A/D value
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Re:A bit confused
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Date: 2006/04/04 17:37
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By: streddy
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Status: User
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Karma: 0
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| Posts: 7 | |
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My partner on this project developed this code for putting the results of the ADC in PORTA and PORTB (used a post from forum.microchip.com website). How does it look? From here the contents of PORTA and PORTB will be uploaded:
| Code: |
void main(void)
{
while(1)
{
TRISA= 0xFF; //tri-state buffer for Port A, all input
PORTA= 0x00; //initialize 8 pins to low
TRISB= 0x00; //tri-state buffer for Port B, all output
PORTB= 0x00; //initialize 8 pins to low
//Setting up the A/D converter
OpenADC(ADC_FOSC_32 & ADC_LEFT_JUST & ADC_8ANA_0REF,
ADC_CH0 & ADC_INT_OFF);
SetChanADC(ADC_CH0);
ConvertADC(); //start conversion
while(BusyADC()); //wait for completion
PORTA = ADRESH;
PORTB = ADRESL
CloseADC();
}
}
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Re:A bit confused
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Date: 2006/04/04 18:20
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By: Mat
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Status: Admin
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Karma: 7
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| Posts: 211 | |
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Looks almost there, but i have a few suggestions.
Why are you putting the output onto PORT A and B, you could just store it internally in the PIC and upload it?
Also you set PORTA to input and are trying to write the result to it? This shouldnt allow the pic to display the result on the port, if your intention was to display it externally.
Mat
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Re:A bit confused
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Date: 2006/04/04 21:25
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By: streddy
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Status: User
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Karma: 0
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| Posts: 7 | |
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Thanks for the suggestions.
When you say to store it internally in the PIC and upload it do you mean in the USB buffer RAM space? If so how is that done?
As for your second suggestion, it was a mistake on our part to set the output on PORTA after defining it as an input.
Please excuse my trivial questions...just trying to understand,
Thanks
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Re:A bit confused
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Date: 2006/04/04 21:34
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By: Mat
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Status: Admin
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Karma: 7
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| Posts: 211 | |
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Just define a variable and save it to that. Look throught he code and you will see lots of examples of how to create variables.
Mat
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Re:A bit confused
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Date: 2006/04/04 21:40
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By: dariog
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Status: User
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Karma: 6
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| Posts: 107 | |
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agreed on it all.
store it/them in the buffers used by HidTXBuffer (or eqv)
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Re:A bit confused
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Date: 2006/04/05 01:04
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By: streddy
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Status: User
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Karma: 0
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| Posts: 7 | |
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Something like this?:
| Code: |
#include <p18f4550.h>
#include <stdio.h>
#include <stdlib.h>
#include <adc.h>
#include <delays.h>
byte LO_BYTE;
byte HI_BYTE;
void main(void)
{
InitializeSystem();
while(1)
{
TRISA= 0xFF; //tri-state buffer for Port A, all input
PORTA= 0x00; //initialize 8 pins to low
//Setting up the A/D converter
OpenADC(ADC_FOSC_32 & ADC_LEFT_JUST, ADC_CH0 & ADC_INT_OFF);
SetChanADC(ADC_CH0);
ConvertADC(); //start conversion
while(BusyADC()); //wait for completion
HI_BYTE = ADRESH;
LO_BYTE = ADRESL;
CloseADC();
}//end while
}//end main
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Re:A bit confused
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Date: 2006/04/05 09:24
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By: Mat
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Status: Admin
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Karma: 7
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| Posts: 211 | |
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Looks better I'd probably make a few changes,,,
| Code: |
#include <p18f4550.h>
#include <stdio.h>
#include <stdlib.h>
#include <adc.h>
#include <delays.h>
byte LO_BYTE;
byte HI_BYTE;
void main(void)
{
InitializeSystem();
//Setting up the A/D converter
OpenADC(ADC_FOSC_32 & ADC_LEFT_JUST, ADC_CH0 & ADC_INT_OFF);
SetChanADC(ADC_CH0);
TRISA= 0xFF; //tri-state buffer for Port A, all input
PORTA= 0x00; //initialize 8 pins to low
while(1)
{
ConvertADC(); //start conversion
while(BusyADC()); //wait for completion
HI_BYTE = ADRESH;
LO_BYTE = ADRESL;
}//end while
}
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put the closeadc() on the loop exit if you ever need it. There is no point in resetting up the tris and ADC each loop as they will be set from the previous one, so I moved it outside the while. Mat
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