Interfacing a Barcode Reader Through Usb with Pic18f4550

[altanonat]

Hello all!

I am trying to interface a barcode reader with pic18f4550, which is an hid device, through usb connection. However I do not know where to start and I do not have any experience about USB. I have looked at examples, but nearly all of them are for interfacing a pic with pc.

First of all I think I need to setup a hid device driver into the pic18f4550, then using an interrupt I need to get a 11 byte string from barcode reader and put this string into an lcd.

I am waiting for your suggestions and advice.

Thank you in advance.

[Ttelmah]

You won't.
Your device, is a _slave_ device.
So is the PIC.

There needs to be a master device, to carry out the transaction. The 4550 hardware can't do this.

Two possibilities:
1) Find a PIC supporting USB 'OTG'. This implies there is hardware support for a master. Then you need to write master software to handle the slave. Unfortunately none at present for CCS. There is a stack for the MicroChip compiler.
2) Add a USB host device, like the FTDI Vinculum. Disadvantage - another device. Advantage prewritten master code is available, and several people here have already interfaced this to the PIC.

Best Wishes

[altanonat]

[bkamen]

You could look to a PIC with USB OTG which should work as a host.

I believe the PIC24's have this capability and the PIC32 definitely has this capability.

Cheers,

-Ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D

[altanonat]

Can a usb to rs232 converter be a solution?

[Ttelmah]

Not really. This is another slave.
However if the barcode reader supports RS232, then the PIC can talk to this, with just a MAX232 buffer chip. Much easier.

Best Wishes

[altanonat]

[Ttelmah]

In which case, get the RS232C cable for it, add a MAX232 to the PIC, and use RS232. Easier, and code size will be several KB smaller as well. :-)

Best Wishes

[temtronic]

Go the easy way, use RS232 ! intstead of the Useless Serial Bus !!

[Ttelmah]

In which case, get the RS232C cable for it, add a MAX232 to the PIC, and use RS232. Easier, and code size will be several KB smaller as well. :-)

Best Wishes

[altanonat]

[bkamen]

[Ttelmah]

It's 'historical'. RS232/CCITT C24, is the 'full' title. The _current_ standard, is actually RS232D. The changes in D, don't affect the signalling as such, but add things like loopback testing. Generally anything _properly_ calling itself 'RS232', will be compliant with RS232C. Unfortunately, there are a lot of interfaces 'purporting' to be 'RS232', that don't actually meet the signalling standards at all (a lot of laptop computers and USB interfaces, use a 'near working' subset of the voltages required....).

However I'm puzzled as to your question. You don't need a 'converter'. You need the cable for your barcode reader, that allows it to be interfaced with RS232. Then you just need the MAX232 (or equivalent) line driver, to allow this to connect to the PIC. No 'converter'. USB won't be involved at all.
The processor on the barcode reader, is almost certainly something like a PIC, and it detects the signals present on the cable to switch to different signalling modes (like modern keyboards, which connect directly to USB, or with an adapter plug, can connect to PS/2 ports - the adapter does nothing, except pull a line 'down' to tell the processor to switch to PS/2 signalling, rather than USB.

Best Wishes

[altanonat]

[PCM programmer]

How do you propose to make the USB-to-RS232 cable work as a USB host ?
All the cables that I have seen for sale, are USB slaves. They must
plug into a USB connector on a PC. The PC is the USB host.