Connect a battery-powered arduino to FTDI USB

Forum 2005-2010 (read only) Hardware Interfacing
1

I have a battery-powered standalone arduino project that stores some data to its SRAM. I will need to connect it to FTDI to upload data to PC. I can't power it down as the content will be lost. So while it's powered by battery, I will connect its RX, TX, GND, RST to the FTDI (basically my deumilanove with its atmega removed). This is ok right now but if I use an FTDI USB cable (FTDI Cable 5V - DEV-09718 - SparkFun Electronics) to tidy my project then I will have to disconnect the 5V on the cable, right? Or otherwise I connect the 5V from my standalone with the 5V on PC the battery may die.

Am I correct? Thanks.

2

It's not exactly clear what the problem is. Can you not just omit the +5V wire from your standalone project to the FTDI cable? I mean, you can put the whole connector there but just not wire anything to the +5V pin.

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3

That would be a good idea for my PCB revision! I was thinking that if I kept it I could power my standalone with the FTDI cable when I want to flash ram.