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USB to Serial converter- driver needed

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snaffer

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USB to Serial

I want to write a code in vb6.0 using usb to serial cable using mscomm control in vb ,my code is working correctly without usb cable .i want to use usb cable through serial port cable connected to it.I am using USB Serial Adapter for it by i don't have DrIVER FOR IT WHICH IS asked when it's connected to pc.
Can iget some hlp .
 

laktronics

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Re: USB to Serial

Hi,
Try the USB to Serial manufacturer's site, you may get it there.
Regards,
Laktronics
 

snaffer

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USB to Serial

hi,

i already installed the driver for this.
ive test the connection using hyperterminal software and communication successfully done. but the problem occur only when i try to communicate with my diagnose software.
is anybody can help me with this?
please msg me if u dont clear with this.

tq
 

FvM

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Re: USB to Serial

What's the exact problem and possibly error message?
 

snaffer

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Re: USB to Serial

Firstly i want to tell about how i establish the connection.
First,i connect the USB to DB9 cable to my laptop. i already install the driver and
its just works fine. Than, from DB9, i connect it to the circuit like i attached (label JP1). The problem is, when i connect using this cable, the transmit and receive process cant be done. i Cant get the "id" message. i have test this using another laptop that already have build in serial port and i just works fine.




 

FvM

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Re: USB to Serial

If the the MAX232 is actually connected as shown in your circuit, it won't work, cause the voltage doubler capacitors are replaced by shorts. No idea, if the device would bear it for longer time without permanent damage. I suggest, to use the circuit given in the datasheet!

If the circuit would be correct unlike the drawing, you should be able to communicate at least through Hyperterminal. With wrong MAX232 wiring, it could be that operation depends on RS232 driver strength, which could be different with USB adapter. However, any problems of this kind would reveal by checking the RxD and TxD lines for correct level.
 

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USB to Serial

this evening i checked the voltage at the DB9 pin, at pin
2 and 3. i want to ask why it give the negative voltage?

than i test the voltage in 2 condition.

1. i checked the voltage at pin no 2 and 3 for connection using usb. than for pin no 2 i got -8.16v and pin no3 i got -8.67v. and for this condition, i cant
communite with my diagnose software.

2. i checked the voltage at pin no 2 and 3 for direct connection from build in serial port at my laptop and i got voltage for pin no 2 equal tu -8.16v but for pin no 3 i got -5.13v and this connection can successfully communicate with my diagnose sw.

question: is it possible for me to use the voltage divider for the pin no 3 (referring to 1 condition) so i cant get the voltage equal to ~-5.13v? i assume this is the solution for this.

2 question: did i need to consider for internal resistance (from the converter)?
 

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Re: USB to Serial

The different voltage levels are simply irrevelant, cause they are all legal RS232 levels. You should have a positive level (arround 5 V) at the logic level interface with negative RS232 level.

When you pull down the bidirectional UART line to ground, RS232 TxD (Pin 2) should rise to a value between +3 V and +12 V. When you apply a positive level to RS232 RxD (Pin 3), the bidirectional UART line should go to a low level and Pin 2 should echo the change.
 

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