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Author Topic: Prolific USB to serial Problems  (Read 9489 times)
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icecubetray
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« on: April 26, 2009, 10:20:49 22:20 »

I'm using a PIC 18F4685 running 8Mhz w/ 4x PLL at 32mhz.  I'm using the CCS compiler.  I also have a Max233 in the mix as well.
#use rs232(baud=38400,parity=E,xmit=PIN_C6,rcv=PIN_C7,bits=8,STOP=1,stream=PC)

I'm using the printf("") to send my string data back.

My PIC application works fine with a normal(real) serial port on my desktop. 

But when I use my Prolific usb to serial converter I have a problem receiving data from PIC.  The PIC receives my command fine from the PC via the Prolific, but the data sent back from the PIC to the PC becomes all garbled.

I've tried several versions of the prolific driver as well without any luck.

I've tried several PC side applications as well with all the same result.

Any ideas? I'm kinda stumped.....as to what the problem might be.
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oldvan
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« Reply #1 on: April 27, 2009, 07:32:44 07:32 »

Have you tried communicating from the onboard serial port to and from the USB addon one to see if the data makes it both ways?

If it doesn't, the problem is the USB serial port.

If communication is fine between the two serial ports, we need to look into PIC side of things.
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« Reply #2 on: April 27, 2009, 05:48:00 17:48 »

I'm using a PIC 18F4685 running 8Mhz w/ 4x PLL at 32mhz.  I'm using the CCS compiler.  I also have a Max233 in the mix as well.
#use rs232(baud=38400,parity=E,xmit=PIN_C6,rcv=PIN_C7,bits=8,STOP=1,stream=PC)

I'm using the printf("") to send my string data back.

My PIC application works fine with a normal(real) serial port on my desktop. 

But when I use my Prolific usb to serial converter I have a problem receiving data from PIC.  The PIC receives my command fine from the PC via the Prolific, but the data sent back from the PIC to the PC becomes all garbled.

I've tried several versions of the prolific driver as well without any luck.

I've tried several PC side applications as well with all the same result.

Any ideas? I'm kinda stumped.....as to what the problem might be.

parity=E   you have parity enabled
surely it should be  parity=1
also perhaps your streem doesnt take parity into account bi dir
as the target port may not be set to allow parity coms
in this case the usb interface

there maybe an adjustment in its driver applet to allow parity
as it may not be driver file rx tx deep
try adjusting the driver for the virtual serial thing

i use a serial hub for comvdd  too allow you to use an adjuster and  tag on another adjuster  instance
within the same simulation
handy for psus  it means you can have two vairents of a circuit running and adjust both at once
however if i use parity i must adjust the hub cable

just a thought...
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icecubetray
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« Reply #3 on: April 28, 2009, 12:28:21 00:28 »

Ya Parity is actually set to none...I forgot to set that back before pasting....

It turns out my max232 chip is oscillating on the tx back to the PC, and hence likely causing some problems

PC serial port to USB to Serial works fine, thanks for the idea....sometimes I overlook simple tests....
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oldvan
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« Reply #4 on: April 28, 2009, 01:06:55 01:06 »

It turns out my max232 chip is oscillating on the tx back to the PC, and hence likely causing some problems

PC serial port to USB to Serial works fine, thanks for the idea....sometimes I overlook simple tests....

Toss a 0.1uF ceramic and a 10 uF tantalum bypass capacitor across its power supply, see if it behaves better.

Don't forget the pretty red star upper right of posts is correct way for ThankYou activity.
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icecubetray
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« Reply #5 on: April 28, 2009, 02:56:18 02:56 »

turns out I missed one of the ground pins on the max 233....... Shocked
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« Reply #6 on: January 14, 2010, 02:59:19 02:59 »

i still have this problem ; PIC to PC using Prolific usb to serial converter received all garbled, i'm using max232 chip at PIC side. this only happen at notebook usb port, the real comm port at notebook and my desktop computer comm are working perfectly. even usb port at desktop working if i put charge bump capacitor to 16uf(max232), EXCEPT NOTEBOOK USB PORTS. lenovoG450;asus; have try not working for Prolific usb to serial converter using PIC but working with mouse.

i suspect problem without receiving buffer at USB driver ; or b.rate handling issue at usb; or buffer issue at usb driver ?.

did anybody encouter this problem before ? any susggestion? buy a USB converter with buffer type ?
   
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« Reply #7 on: January 14, 2010, 02:56:08 14:56 »

I have had the same problems with that type of converter. I went with using a FTDI USB-rs232 converter and that worked perfectly.
I did find a Prolific converter that did work later that I purchased from RadioShack. My guess some of those converters are not designed properly and
may have buggy windows drivers.

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« Reply #8 on: January 14, 2010, 06:42:56 18:42 »

Hello,

I have read some where that, there some problems when using default configuration for windows COM buffers.

To change default values, you need to go in windows device manager, go on the COM Port, right click,

properties, click on Advanced, and put Rx Buffer to 1, and receive Buffer to 1.

It also works for FTDI and Prolific converter which have sometimes the same problem.

Remark: In this page, you can change the Number for COM Port.

These hardcopies are on a French Windows, but i think every body can find easily the same buttons on his Windows.

Best Regards.
« Last Edit: January 14, 2010, 06:48:49 18:48 by titi » Logged
oldvan
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« Reply #9 on: January 14, 2010, 06:54:32 18:54 »

I have had the same problems with that type of converter. I went with using a FTDI USB-rs232 converter and that worked perfectly.
I did find a Prolific converter that did work later that I purchased from RadioShack. My guess some of those converters are not designed properly and
may have buggy windows drivers.

I bought a 5-pack of the cheapies on eBay a while back.  None worked.
Disassembled one (was potted in plastic, not a fun task), turned out only pins 2 and 3 of the DB9 were connected to anything,
not a GND in sight.  I tossed them out, picked up a couple at BestBuy and finished the job.
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« Reply #10 on: January 15, 2010, 04:01:59 04:01 »

i've thinking to make a converter myself, do some research and finally i make it work now.
i bought a new and cheap converter from HK, vztec.com "VZ-UC1052", but without vista driver, i think is old stock,  google & download few others prolific driver from others site that claim working with "VCP"; PL-2303 chip set.  wah-lah...one of the driver is working good. Grin Grin Grin.

since i've do some research and some raw info collected, such as schematic; PCB; drivers, 2 differance chipset datasheet;...etc; for someone who interested on this can download at below link, i think is usefull if u have  Prolific USB to serial Problems, at least, save u time to google it. if u like it press"thankyou" button.

http://rapidshare.com/files/335170227/USB_serial.rar

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king
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« Reply #11 on: January 29, 2010, 11:46:37 11:46 »

Hi!
This may also be possible that your prolific usb to serial cable is ok but something is wrong with your circuit so for this you simply have to generate the serial data with the help of microcontroller without using ICSP and check that your hyperterminal is receiving data or not

Regards

King

Posted on: January 29, 2010, 11:44:43 11:44 - Automerged

Hi!

Try this Driver may be your problem will be solve by this
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oldvan
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« Reply #12 on: January 29, 2010, 02:02:15 14:02 »

...so for this you simply have to generate the serial data with the help of microcontroller without using ICSP and check that your hyperterminal is receiving data or not

Can you please elaborate?  I don't see how ICSP or not is relevant to serial port issues.
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