Hello, If you are able to solder some electronic devices, you can do this quite simply. To convert the +3.3v to a +5V for the TX line, you have several solutions : - use two logic inverters working at TTL levels ( for example a 74LS04 contains 6 inverters). power the device at +5V, share the grounds. It will see the +3.3 as a logical one ( the threshold is around 2.5 volts). You need to cascade two inverters to get back in phase - use a npn transistor, just having a simple low restistor on the base gate.
To convert the +5v to +3.3 ... add two small diodes in the line, each drop the voltage by approx. 0.7 volts Hoping this helps sylvain 2009/9/22 [email protected] <[email protected]> > > > Hello everybody, > > ... I tried searching the web, searching the ACME systems home page, and > searching through this group - but unfortunatly, I did not find an answer to > my question. So my last hope is that someone here already faced this > problem. > > I want to connect a small medical device to the foxboard. This device > provides a serial connection based on a 5V-TTL-Level. At the moment, it is > connected to /dev/ttyS0 using the FOX console ( > http://foxlx.acmesystems.it/?id=106) on foxboard-side, and > TTL-to-RS232-converter on the medical device side, so that the > "architecture" is medical device <-> cable to TTL/RS232-converter <-> > crossed cable to the FOX console <-> foxboard J10. The whole thing works, I > can communicate and exchange data with the attached device - but of course > this is not really a "nice" solution because of the two converters involved. > That's why I would like to directly attach the medical device to the > foxboard - according to the documentation, the foxboards serial ports on J6 > are 5v tolerant, so I guess that I at last could try to connect my device to > that port without causing any damage. Unfortunatly, ! nothing is said about > the port realized at J10 - I *guess*, that this also should be 5V tolerant > (why should only J6 be?). Can perhaps anyone here confirm (or negate) my > assumption? > > Secondly, what I'm asking myself: it is one thing that this port is 5V > tolerant - so I may send in signals on the RX line, and the foxboard will > know how to handle those data. But of course, I will need 5V on the TX line > too to ensure that the device on the other end of the line can handle the > signals send from the foxboard. It my assumption correct that the foxboard > will send signals at 3.3V level, and that it is not sure that my device > attached at the other end of the line will be able to work with those > signals? (sorry for this stupid question - I'm computer scientist, but this > seems more to be a problem for an electrical engineer ;-)). > > Thanks in advance, and greetings from Dortmund University, Germany > Jan > > >
