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data aquisition system using usb port

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rupesh58

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i m working on project data aquisition system using usb port . i m intrested in using pic 18f4550 microcontroller chip to connect adc0808. but i m confused about the purpose of digital outputs pin. plz, tell me wher i need to connect those pins. plz suggest me the way as soon as possible.....
 

DineshSL

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Hi rupesh58,

Pin 19..22 & 27..30 in 18F4550 belongs to PORTD. They can be used as digital Inputs or Outputs.(see datasheet of 18F4550)

It is easy if you connect output pins of ADC0808 to any 8-bit port of 18F4550 (ie PORTA, PORTB or PORTD)

By the way, you can use 10-bit ADC module in 18F4550; it has 13 inputs.

Thanks,
 

rupesh58

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Thankyou sir, for your suggestions. but still i want to know some key informations:-

1.If i m using adc 0808 then wat is d purpose of digital outputs (pins 19-22 & 27-30)
because u hav told that they can b connected to PORT-D & usb is receving inputs from pins 23 & 24.

2.If v r not going to use adc0808 then from wher we provide the digital inputs
(pins 33-40).

3.If we use both adc0808 & pic 18f4550 then ther may be some freuency conflict ?
if it does then how will we solve this problem.

4. Wat is D+ and D- in usb connector?

plz , reply me as soon as possible.
 

karesz

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Hi,
Sorry, I think if you wish to develop some thing for a Bus system (i.e. USB), to first you have to read the spec`s of the goal Bus-system!
USB has diff. data transmission, as such a system calls (of course) the diff lines: D+ & D- ...
Good progress!
K.
 

DineshSL

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Hi rupesh58,

1. pins 19..22 & 27..30 at 18F4550 have nothing to do with USB. They belong to PORTD of PIC (read data sheet of 18F4550)

2. If we don't use adc0808 means no digital inputs to 18F4550, hence leave those pins alone (pins 33..40 or whatever)

3. They can use separate clock sources;
According to "Functional Description" in data-sheet of adc0808
first select analog channel then give start-conversion signal and wait to receive end-of-conversion signal and after that, read output data pins.

4. read https://pinouts.ru/Slots/USB_pinout.shtml

Thank,
 

Kurenai_ryu

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Maybe you can use an smaller pic like the PIC18F2550, it still has in-built ADC, the 8-bit PORTB for Input so you will have fewer unused pins...

don't forget that you can connect the adc0808 digital outputs to any digital inputs on the PIC., better if they are from a single PORT also, you must connect the control signals (latch enable, address bits, and output enable) to any available digital ouptuts on the PIC.

any way...
i think that you are using a development board for usb (the one from sixca http://www.sixca.com/eng/articles/usbdaq/index.html)... why didn't you say that?????

you can do whatever you want with the available digital inputs, and outputs, it uses the in-built ADC, so mostly you don't need them...
 

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