usb interfacing from pic to PC

nidhimittalhada · Joined: 06 Sep 2010 Posts: 21

I have pic development board

http://www.rhydolabz.com/index.php?main_page=product_info&cPath=99_101&products_id=297
in which I give power to board through usb port from PC.

Now I want to learn interfacing PIC18f4550 through usb to PC.

How should I start?

I have no knowledge about USB interface /protocol/device.
Please guide me from start...

Nidhi

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

The CCS compiler has many examples of using an 18F4550 with USB:

nidhimittalhada · Joined: 06 Sep 2010 Posts: 21

#include "18F4550.h"

#fuses HSPLL, NOWDT, NOPROTECT, NOLVP, NODEBUG, USBDIV, PLL5, CPUDIV1, VREGEN

#use delay(clock=48000000)

#include <usb.c>
void main()
{
int8 new_enumerated;

usb_init();
set_tris_b(0x00);
while(1)
{
new_enumerated=usb_enumerated();
if (new_enumerated)
{
output_high(PIN_B1);
delay_ms(2000);
}
else
output_high(PIN_B3);
}
}

This is my code , just starting code for testing device enumeration.
But it on compilation gives error

Error 23 "C:\Program Files\PICC\devices\18F4550.h" Line 2(8,9): Can not change device type this far into the code

I have tried removing include 18F4550 line from my main file also , still this error persists .

pl help , what can be cause of this error!!!

thanks

Ttelmah · Joined: 11 Mar 2010 Posts: 19496

You have something else 'in front' of what you have posted.
Basically, this error occurs, if you have any code that changes the device type _after_ something else that sets or uses the device type. What you have posted, compiles _without_ this error. So you have something (an include, a device statement, almost anything!), in front of what you have posted.
Are you compiling this in CCS, or using another environment like MPLAB?. If the latter, you could also get the error if something is being included by the development environment, before this code.

Comment, use the code buttons. Makes code much easier to read!....

Best Wishes

nidhimittalhada · Joined: 06 Sep 2010 Posts: 21

Hi
I have resolved that problem of header file inclusion in proper sequence.
But now the other problem is

When I build all files in project -- it says BUILD FAILED. Error is
Undefined identifier -- usb_enumerated
but I have included usb.c as shown in file tree I am printing below.

I am using MPLAB 8.53 and My file tree shows
Source Files
usb.c
usb_main.c
Header File
PIC18F4550.h
usb_desc_hid.h
usb.h
pic18_usb.h
usb_main.h

Object Files

other file
usb.osym
usb_main.sym
usb_main.sym

I am showing you the file structure where in usb.c is standard library and usb_main.c is my program.

sturnfie · Joined: 26 Apr 2010 Posts: 17 Location: Palatine, IL

nidhimittalhada · Joined: 06 Sep 2010 Posts: 21

we copied pasted your code and in header files included
18F4550.h
usb_cdc.h
nothing else
Now it gives familiar error
Cannot define Device so far in the code --- error points to 18f4550 line #DEVICE

which we were also getting in our case too...then we tweaked inclusion of files in usb.c to remove this error.

nidhimittalhada · Joined: 06 Sep 2010 Posts: 21

Source Files
try_usb.c -----------> this program given by you
Header Files
usb_cdc.h

Now
i do project build all in MP LAB
and error comes is

*** Error 23 "C:\Program Files\PICC\devices\18F4550.h" Line 2(8,9): Can not change device type this far into the code
*** Error 48 "C:\Program Files\PICC\devices\18F4550.h" Line 190(2,6): Expecting a (
*** Error 48 "C:\Program Files\PICC\devices\18F4550.h" Line 190(18,23): Expecting a (
*** Error 43 "C:\Program Files\PICC\devices\18F4550.h" Line 190(0,1): Expecting a declaration
*** Error 51 "try_usb.c" Line 39(37,38): A numeric expression must appear here
*** Error 79 "try_usb.c" Line 39(37,38): Expect }
*** Error 79 "try_usb.c" Line 39(37,38): Expect }
*** Error 79 "try_usb.c" Line 39(37,38): Expect }
*** Error 79 "try_usb.c" Line 39(37,38): Expect }
*** Error 75 "try_usb.c" Line 39(37,38): Expect WHILE
*** Error 79 "try_usb.c" Line 39(37,38): Expect }
11 Errors, 1 Warnings.
Halting build on first failure as requested.
BUILD FAILED: Sun Sep 19 22:09:30 2010

sturnfie · Joined: 26 Apr 2010 Posts: 17 Location: Palatine, IL

Don't add usb_cdc.h directly to the project. Pull it in-line as per the example. Only add this "try_usb.c" to the project. Then build the project. The code I posted does have a typo, it is missing a closing ". Double click the error to find the line, and change the code to match this:

sturnfie · Joined: 26 Apr 2010 Posts: 17 Location: Palatine, IL

Btw, you'll get this when the build succeeds. Use the search feature on this forum to learn why you get these warnings (they can be safely ignored).

Douglas Kennedy · Joined: 07 Sep 2003 Posts: 755 Location: Florida

Well if you are new to the PIC and new to usb this will prove to be very challenging. Most start simple then go complex in this case complex is the usb interface. Usb has a sequenced set of commands and strict timing any one of which just slightly off will result in failure. The PIC code itself can be complex partly because it addresses the complexity of usb and partly because it is written so as to be portable to different pic devices via includes and defines. Doing something simple like blinking leds and timers will start getting you acquainted with the includes and defines found in main and the xxxx.h files.
With skill gained with the compiler issues then move onto usb. If a compiler message shows up chances are you are already familiar with it.

asdf85 · Joined: 03 Jan 2011 Posts: 34

I've been trying to get the PC to recognize the USB connection with my pic, but all the examples I try doesn't work.

I'm using a pic18f25j50 with a 20Mhz crystal, trying to connect to windows 7. My compiler version is 4.093.

I tried Sturnfie code here also and it doesn't work. Everytime I plug the USB cable into the pc, there's a notification saying 'USB device not recognized'. What am I missing? I did download the 'Microchip Application Libraries V2011-12-05' thinking there are drivers there, but I can't seem to get any recognized.

This is Sturnfie's code which I adjusted slightly due to the different PIC used:

temtronic · Posted: Thu Jan 12, 2012 6:26 am

CCS supplies the required 'Windows stuff' needed for it to recognize and 'connect' to their examples.
The CDC example does work fine as written,I'm using an 18F4550.
USB is a real 'challenge' compared to 'old school' Comports! The USB overhead takes up 1/3 of the memory space of an 18F4550 so I'm really leaning towards using Vinculum-II 'modules' to recover the memory,have BOTH Host and Slave ports and get the product out the door faster.
The nice thing it sames TONS of time and money but for home use the onboard USB does work. Get the 'serial CDC ' example running first, then carry on..

sturnfie · Joined: 26 Apr 2010 Posts: 17 Location: Palatine, IL

asdf85 · Joined: 03 Jan 2011 Posts: 34

When I try updating the driver with the 'CDC_NTXPVista.inf' once windows states ' usb device not recognized', it does show 'USB to rs232' in the update driver screen. However when i click next to install, windows will state 'Windows encountered a problem installing the driver software for your device. Btw I am using a 32bit windows 7.

I would also like to know, if i make a simple program with just 'usb_init_cs(); ' followed by a 'usb_task();' , is that enough to get the usb device recognized or enumerated by windows in most cases?