Help needed on MAX 232

Hi all ,

I have built a circuit(schematic on the link) using MAX232 to convert TTL to RS232. I found this on a site "http://sodoityourself.com/max232-serial-level-converter/". After building the circuit when I plug that nothing happens. In the device manager there is no new driver or COM port installed. What I want to know is that when using MAX232 do we need any drivers as there are drivers for some converter cables.

Please need some guide on this

Thanks
Nuwan

Hi

Normally It is not detected when you plug to the PC and no need any drivers

try simple test like "loop back"

Give some input command to your serial port and read echo output

regards
bassa

irrespective of you connect any device or not.... comport should be identified at any time, in device manager or hyperterminal configuration.... you should be able to view the com port number in device manager.....

without connecting max232.. you should view it.....

if you are using a USB-Serial cable then it may need a driver, because these are having unique drivers that are not loaded to OS kernel by default.
but if you are using normal 9 pin DB-9 port for serial communication then no need for drivers, as these drivers are always loaded to kernel, and it always shows the COMPORT in device manager.

but for usb-serial converters it loades the driver hence the COMPORT (device manager) when the device connected.
but for usb based serial cables you do not need a MAX232 because it is already at ttl level.

Hi guys,

Thank you for your quick responses, but I forgot to tell whatz going on currently. I have windows 7 and a Laptop which doesn't have COM ports so as "asimkumar" has mentioned that there are built in COM ports I don't have in my laptop. So in the device manager it will not show any. I tried the Prolific and FTDI usb drivers, even though it doesn't detect the circuit and COM, ones plugged to the USB the its says "Unknown Device" in the device manager.
Does any one have built any circuit like this? or similar? to convert from USB to COM

Regds
Nuwan

It's completely mysterious, how you connect a MAX232 without a built-in COM port or an USB-to-COM bridge chip. Please clarify.

Ah? Sorry I didn't get what you said.. What I'm doing to connecting the TTL side to the USB port and get the out from the RS232 side using a DB 9 connector.. Even I'm using the voltage from the USB port (5v) to the MAX232 input voltage.
Am I doing something wrong?

Not so simple to implement. :grin:
You need to use also a hardware circuit with channel bridge features, able to be configured for asynchronous and synchronous serial standards. See the FT232 application. Virtual COM port (VCP) drivers cause the USB device to appear as an additional COM port available to the PC. Application software can access the USB device in the same way as it would access a standard COM port.

http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf



See also a link for another simple implementation USB to RS232 converter into single chip microcontroller:
**broken link removed**

I think, to understand why you can't directly connect a rs232 to the USB interface, it would be helpful to get a rough idea what USB is. Much information is available from this side: **broken link removed**

use a USB to RS232 cable and install that driver .....then the port can be seen selected..

Hi
many micro controller have usb such as PIC 18F4550 and the other must convert serial (RS232) or etc to usb (Universal Serial Bus) standard by many chip like FTDI (ft232 ...).
If you want to use FTDI chip for interface usb and com then you need to install it's drivers. however you can find com to usb converter easily.

The simplest technique to connect your chip is to buy a usb-serial cable INR150/- (~3US dollar)(available at computer peripheral shops)
connect it to usb port, it will ask for drivers which you will get in the CD with cable .

Just connect the pin2 and 3 of the DB9 side of the cable directly to your chip (no need of MAX232)

Hi Guys,

I think my description made you guys confuse. Or I might be telling something wrong..
Let me explain, I am have build a USB to Serial converter circuit (same as the usb to serial cable). See the link and the attached image link. "http://sodoityourself.com/max232-serial-level-converter/", "http://sodoityourself.com/wp-content/uploads/2007/02/circuit_232.jpg".

Here they have build the usb to serial circuit which is shown there. But when I plug that to my USB port it doesn't get detected as a normal USB to Serial cable. What I'm asking is that do we need a driver for this as we need a driver for the usb to serial cables which are there in the market to purchase? If so what is that driver as I have tried Prolific and FDTI, nothing detects the circuit as a USB to Serial device, it show as a "Unknown device" in the device manager.

I think I have build the circuit correctly but don't know where to go from there because even if I wrote to the person who has built the circuit still didn't get any response
Guide me if I'm doing something wrong here.. Thank you

Help is much appricated
Regds
Nuwan

None of the links is showing an USB interface.

There should be a Prolific chip (e.g. PL-2303) to work with the Prolific driver or a FTDI chip (FT232) to work with the FTDI driver. As already mentioned, buying the complete cable in a computer store next door would be the most easy option.

NuwanR said:

Hi Guys,

Let me explain, I am have build a USB to Serial converter circuit (same as the usb to serial cable). See the link and the attached image link. "http://sodoityourself.com/max232-serial-level-converter/", "http://sodoityourself.com/wp-content/uploads/2007/02/circuit_232.jpg".

Click to expand...

Your link shows a standard serial converter between the PC RS232 plug and the MCU UART, there it no USB involved anywhere in that.

NuwanR said:

But when I plug that to my USB port it doesn't get detected as a normal USB to Serial cable.

Click to expand...

So you have actually connected the RS232 to the USB plug of your PC :!:

your circuit is supposed to be connected like this


but you don't have a serial plug in your PC so one solution you can use is to buy a USB to RS232 cable


Alex

Thank you guys for your guidance
Will try to make one using a suitable chip & a schematic

Regds
Nuwan