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USB Data acquisition with PIC18F4550
This project is simple and small component count USB data acquisition or USB DAQ.
The
main core of USB device is PIC18F4550 .The
firmware for PIC
modified from Microchip CDC library.
I use Delphi 6 on PC side to communicate with PIC18F4550
source code availible.
Specifications
- 8 Digital output
- 8 Digital input
- 8 Analog output
- No external power required
- Simple ASCII command
- 3 command to communicate PC with PIC
Figure 1 Schematic
Command
Command PC Send PIC respone
Write digital output *ANS#13 -
Read digital input
*B#13 *BHH#13
Read analog input *AK#13 *AKXXXX#13
When :
N = bit that we need to set or clear (0-7)
S = state of bit (0-1)
HH = Input status from digital input port (00-FF)
K = Channel of analog input (
0-7)
XXXX = analog input value in decimal of 10 bit binary (0000-1023 )
#13 = end of command
Example to set bit 0 of digital output
*A01#13
Example to clear bit 0 of digital output
*A00#13
Example to
read digital input
*B#13
then PIC respone with
*B7F#13
This mean bit 7 of digital input was low
Example to read analog input channel 4
*C4#13
then PIC respone with
*C41023#13
This mean that analog channel 4 have 5 volt on this channel
becuase 1023 = 3FFh
Figure 2 PC side software |
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When connect this USB Data acquisition with PC then windows ask
for driver after driver installed(only first time) you will have a new
COMx if not connect the COMx not create by Windows.
How to set configuration please read this article
Zipped file consist of :
- Firmware examples with source for C18 Compiler
- Delphi 6 example with source
- Windows device driver (Win2K/XP)
source code
Relate articles
Brief USB definition
USB CDC example
Control stepping motor with UCB
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