Take the 2-minute tour ×
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It's 100% free, no registration required.

Currently I have the following microcontroller Atmel 89C61RD2 through a max 232 chip to RS232 interface. I would like to have an extra connection to a USB interface also. How can I do that? I would like to retain the same microcontroller and change only the max 232 chip.

share|improve this question
2  
Go with any USB-Serial converters from FTDI (FT232BR),SIlabs(CP21xx USB to UART bridge family) etc –  user19579 yesterday
    
I cannot find the AT89C61RD2, are you sure it's correct and not AT89C51RD2? –  Camil Staps yesterday

1 Answer 1

This will require a chip quite different from the MAX232, because RS232 and USB is a completely different protocol. Here, there is some more explanation on that:

Although RS232 and USB (universal serial bus) are both serial communication standards to connect peripherals to computers, they are totally different in design. A simple cable is not enough to connect RS232 devices to a computer with only USB ports.

Anyway, a chip that you could look at is the USB-DUO series of FTDI: http://www.ftdichip.com/Products/Modules/USBRSxxx.htm (the credits go to John U in the comments).

Now, there are also microcontrollers that have USB support. That means, they can communicate easily over the USB protocol without an external chip, since they include specific hardware to do this.

However, a look on the information page 1 shows you that this chip does not have any built-in USB support. If it would have supported USB, there would be some lines like 'USB transceiver', like here.

Atmel doesn't have any chips in this series (with the 8051 architecture) that supports USB just like they support UART (RS232). To look for a chip that supports USB, you could use the product search.

But note that if you are going to use a chip with a USB peripheral, you cannot just copy the code and have it working for USB. The software needed is completely different.

Another option, without having to change your current circuit, is using a USB to serial converter. You could use a more common one like here. There are also much smaller types available like this one. You can of course also do it yourself.


1: I'm assuming you meant AT89C51RD2 (a 5, not a 6).

share|improve this answer
2  
I'd say this absolutely IS "just possible by changing the MAx232" because FTDI do chips that provide a USB interface from a standard TTL or RS232 connection on a micro. They even do a DB-9 shaped USB port with driver IC inside that drops in the place of a DB9 serial connector, very handy! Adding full & real USB support to a microcontroller is not trivial unless someone has already written the code and you can adapt it, this varies with device & manufacturer. –  John U yesterday
    
@JohnU oh, you're right! I never knew. –  Camil Staps yesterday
    
They do two versions of the DB-9 - one that takes RS232 levels from a MAX232, and one that takes TTL so you can remove or not fit the MAX232 & bridge the TX / RX lines straight out to the port. –  John U yesterday

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.