Arduino Forum

Using Arduino => General Electronics => Topic started by: SouthernAtHeart on Feb 27, 2014, 04:48 am

Title: Adding a FTDI to my project
Post by: SouthernAtHeart on Feb 27, 2014, 04:48 am
I want to add an FTDI chip to my project so it can be connected via USB, rather than a separate FDTI cable.
So I copied the schematic from the FTDI basic, from Sparkfun, and pasted it into my new project.  
Since I won't be using 3.3 volts, can I delete C1 and the net connected to pin 17 on the FTDI chip? And can I remove the solder jumper SJ2, and then connect pin 4 on the FTDI chip to 5V?  I think this is right, but want to make sure.
After doing this, the 2 schematics will just kinda merge together into one I believe, with the FTDI allowing the USB port to talk to the Atmega chip.
Thanks.


ps.  Also, I see CTS from the FTDI chip will not be connected to anything.  It's ok to leave it unconnected?  The DTR pin is what resets the Atmega chip during programming, right?
Title: Re: Adding a FTDI to my project
Post by: SouthernAtHeart on Feb 27, 2014, 04:56 am
To visualize my question, here is the schematic after I made these changes.  Will this work? 
I'm wondering if the TX & RX pins are connected correctly, though.  Do I need the FTDI's TX pin to connect to the Atmega328's RX pin?
Title: Re: Adding a FTDI to my project
Post by: fungus on Feb 27, 2014, 10:21 am
Another solution is to use VUSB and implement the USB interface in software.
Title: Re: Adding a FTDI to my project
Post by: SouthernAtHeart on Feb 27, 2014, 12:55 pm
Huh?
I don't know what VUSB is. Here's photos of the schematic I'm talking about in case you can't view the PDF files.
The before and after. Please read my first post to see my question.
Title: Re: Adding a FTDI to my project
Post by: MarkT on Feb 27, 2014, 01:18 pm

I want to add an FTDI chip to my project so it can be connected via USB, rather than a separate FDTI cable.
So I copied the schematic from the FTDI basic, from Sparkfun, and pasted it into my new project.  
Since I won't be using 3.3 volts, can I delete C1?


No you cannot do that, the chip is internally 3.3V and relies on that supply.  To quote the
datasheet (which is where such questions are generally answered):
Quote
+3.3V output from integrated LDO regulator. This pin should be decoupled to ground using a 100nF capacitor. The main use of this pin is to provide the internal +3.3V supply to the USB transceiver cell and the internal 1.5k? pull up resistor on USBDP.


So you must provide a decoupling capacitor on that pin.
Title: Re: Adding a FTDI to my project
Post by: SouthernAtHeart on Feb 27, 2014, 01:35 pm
Thanks. I should have checked that. 
I'm pretty sure I have the Rx & Tx connected wrong too.
Title: Re: Adding a FTDI to my project
Post by: graynomad on Feb 27, 2014, 02:13 pm
Quote
I'm pretty sure I have the Rx & Tx connected wrong too.

Yep, Tx->Rx, Rx->Tx.

Also your TX/Rx LEDs are on the wrong pins, swap them. EDIT: Actually I've got examples of schematics both ways, I'll have to check that.

______
Rob
Title: Re: Adding a FTDI to my project
Post by: graynomad on Feb 27, 2014, 02:30 pm
Interesting, both the Duemilanove and the original Mega schematics are wrong, they stuffed up the FT232 pinout. It should be as you have it

TXLED on pin 23
RXLED on pin 22

As you were :)

______
Rob
Title: Re: Adding a FTDI to my project
Post by: CrossRoads on Feb 27, 2014, 02:59 pm
I've found the FT232RL to be difficult to solder to a board, the pin pitch is very tight.
I've gone to using an FTDI module instead for boards I plan to assemble myself (wife & I).
http://www.mouser.com/ProductDetail/mikroElektronika/MIKROE-483/?qs=%2fha2pyFadugsEwyLV5fFyIWdPbushEDhRSvnBE0ODG8%3d
Chip itself is $4.50, so I figure the price of the module with chip, caps, inductor, and mini-USB-B connector is kind of a wash. Still need LEDs & resistor for signaling.