cannot use Nano as ftdi?

For many years I've used an Uno with RST shorted to ground to connect serial ttl devices to computer USB ports - always worked fine.

I decided to do the same thing with a Nano, made a very nice pcb with a switch to ground the RST line one molex socket for the serial line and another for I2C connection so I could use it alternatively as an FTDI, a conventional nano controlled serial connection or a nano based I2C setup.

But alas, the basic function using the shorted RST doesn't transmit reliably to the TTL serial device.

I assume the USART/UART on the Nano must behave differently from the one on the UNO. Is this right?

And if you know, what do I need to look for to remake this thing using another micro-controller that's as small as the Nano?

jferguson4:
I assume the USART/UART on the Nano must behave differently from the one on the UNO. Is this right?

I would not expect it to. However, it may be that your Nano has a different USB to TTL serial chip than your Uno. The official Uno and clones use the ATmega16U2 microcontroller as a USB to TTL serial chip. The official Nano uses the FT232. Derivative Nanos use CH340 (which some derivative Unos do as well). So I suppose the difference could be related to different chips, though I don't have a hypothesis as to why.

jferguson4:
And if you know, what do I need to look for to remake this thing using another micro-controller that's as small as the Nano?

Why not just get a dedicated USB to TTL serial adapter module? You can buy them for $0.75 with free shipping from China on eBay.

Thanks Pert. You're probably right that I should just go buy one, but I suffer from the great engineering tradition of trying to make what you need from what you have.

At this point, the only thing I need it for is configuring Ublox gps's.

regards,