For some reason, my arduino nano is not recognised from my PC. I suspected that it was from the FTDi chip and I was corect (I hope). I connected the arduino to a USB over serial device ( http://www.ebay.com/itm/CP2102-USB-TTL-RS232-Serial-Port-Converter-Transceiver-/230308271855)on the Pins 0 and 1 (Tx/Rx) and I can upload a scetch and see the serial port from there. I have two problems. 1. I have to press reset on the nano just before uploading the scecth and just after the upload ends in order to work ok. I believe the FTDI interface does it by itself when connectedfrom USB 2. I have a scetch that receives ascii chars from the PC through serial and transmit some data back.On the PC there is a VB6 app that sends and receives. (actually it is the The VBterm example) When I used the USB connection it worked fine, but now MSComm control reports an error. But if I use putty with this connection there is no problem. I know that there must be something in settings but what is it? What is different on the serial port when use it from the USB side and when fro the Rx/Tx pins?
1) to auto reset you should connect the DTD pin from the interface to the reset pin through a 0.1uF capacitor.
2) this is probbly due to not having some of the handshaking lines connected together. See if you can change the settings so that hardware handshaking is off.
Thank you. I think the converter does not have a DTD (you mean DTR?) pin. I 'll check it tommorow morninng
(you mean DTR?)
Actually, I couldn't find in my boxes a 0.1 uF capasitor. I tried with a larger one (100uF) and with no capacitor too. I connected the reset pin with a DTR pin on the converter but it didn't work. Maybe the DTR pin of the converter does not work. What is the purpose of the capacitor anyway? I also tried every combination (I think) of settings in the MS comm control but no luck. Perhaps there is a bug in MSCOMM.OCX
When the serial port is initialised the DTRpin changes level. Thecapacitor changes the level into a pulse. They values you tried are way too big for it to work. You need a 0.1 to 1uF cap here.
Ok, I got it now. I still couldn't find a 0.1uF and I used a 1uF capacitor, and it worked perfectly. Thank you for the solution. The other thing is not working though. I tried a VB code that does not use MScomm control . It uses windows API and the problem did not occure, so I gues it is a bug of MSComm.