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Hi, I've been trying to configure my Pluto-II with an FTDI TTL-232 USB-serial converter, but to no avail. The datasheet for the cable is here: http://www.ftdichip.com/Documents/DataS ... S_V201.pdf I have the 5.0V version of the cable.

I've tried plugging the USB-serial cable into the appropriate pins on the TXDI board, and directly into the Pluto board without the TXDI board. Either way, as soon as I connect to the RxD line on the Pluto board, it appears that the FPGA freezes operation -- the onboard LED, which normally pulses on and off just glows a solid dim red. FPGAConf times out when I try to upload an rbf file.

Could anyone give me some tips on how to get this working?

BTXSistemas wrote:Hi nikto.
I did it, I can´t remember now which modifications I did in the Pluto II, but you should do some on this.
Take care and look at the serial input of the Pluto II board, your problem is that some wires are inverted by the CDxxxx chip. If you have an oscilloscope it will be easy, I remember I cut a a wire of the pcb, and put a bridge on a R.
It´s quiet easy.

Unfortunately, I do not have an oscilloscope handy, and to be honest, probing around and modifying my Pluto board is a little outside my comfort level, since I'm still rather new to electronics engineering.

You mentioned that the CDxxx chip inverts some signals -- what if I put a PNP transistor between my TTL-232 cable's RxD line and the Pluto board to invert the signal? Would I also need to invert the TxD line?

BTXSistemas wrote:OK.
Give me some time, and when I'll have some free time, I will check my Pluto board to let you know which are the modifications.
Yes maybe you could invert the signal outside the board, but I'm not sure now....just I said you, there are some modifications in the board.
Maybe it's a good idea if I'll send to you some pictures of "where to touch" the board.

Thank you, I'd appreciate that. I tried inverting the signals from the TTL-232 earlier tonight, but I still couldn't get my Pluto configured. How exactly do the signals coming from a TTL-232 differ from those from an actual RS-232 serial port?

Yes, I have these.

Ok, I think I understand. I've drawn a diagram: http://img291.imageshack.us/my.php?image=diagramed9.jpg Is that correct, or should I connect the Pluto's white wire directly to the FT232's TxD line, bypassing the TXDI?

Ah! Now it works! Thank you very much for your help, BTXSistemas.

Just one more quick question: I use a TTL232, not an FT232, so it uses 5V logic levels, not 3.3V. I've seen other posts here that indicate that the Pluto's RxD line is able to handle normal serial voltages as much as 12V. Is that still the case here, or do I run the risk of damaging my FPGA by using 5V signals? If so, would a higher value resistor on the RxD line protect my board?

I don't understand fully the modification but try to use a 1Kohm resistor when you drive the 4093, it should solve any trouble.