Using a CP2103 to program an ATMEGA328-PU

[revolt_randy]

I'll be the first to admit, I'm not 100% sure I know what I am doing, so I should not doubt you.

@Grumpy_Mike

The mistake you have made is to connect the DTR of the CP2103 directly to the reset pin. In fact it needs to be connected to the reset through a series capacitor, 0.1uF seems normal. This converts the logic level into a pulse and it is this pulse that resets the Arduino. With it connected directly your CP2103 is holding the Arduino permanently in reset.

The CP2103 DTR line is pin 6 of the J2 header. When connected to the clone, it is pin 6 of JP7 header, the RTS# net in it's schematic. It's connected to the 328 RESET with capacitor C6. So I think I have it connected right.

@Grumpy_Mike

The other thing that worries me is that the CP2103 is being powered by 3V3, which means all the signals out are at 3V3 logic levels which technically below the minimum high a 5V Arduino needs, but often you get away with that.

This is what I understand too, you can get away with 3V3.

@Grumpy_Mike

However one thing you won't get away with is that the 5V TX signal from the Arduino is too high for the 3V3 maximum input of the CP2103's RX input. This needs to be cut down with a potential divider, before any damage is done. ( It might be too late for your chip ).

Looking at the CP2103 data sheet, Table 1 suggests it will handle 5.8V on any I/O pin. Or am I not understanding the data sheet?

I do have some logic level converters and could breadboard one in between the CP2103 board and the clone, just to be sure. I think the CP2103 is ok, because it returns Board Info in the arduino IDE. There is a software tool for adjusting it's settings that I have been thinking of using it to see if the chip responds. I'll try these things and report my results.

Thanks,
Randy