I want to make Arduino standalone board with only the things I need (digital & analog pins, no ICSP, no blinking diodes etc) and I'm wondering, how to make my own FTDI board - I'll be honets, buying it is too expensive, I'd rather do it.
I assume, Arduino uses only TX/RX, so I could take this diagram and connect those two with Arduino? So... there's more I'd like to know:
why pin 20 is connected to USB Vcc AND to +5V? Can't it just take voltage from USB?
do I need to connect pin 17 (3.3V)?
what should I do with CTS and DTR pins? Can I just ground the through a resistor?
finally... I assume I connect FTDI's TX (pin 1) to Arduino's RX (ATMega pin 2)?
why pin 20 is connected to USB Vcc AND to +5V? Can't it just take voltage from USB?
There is no 5V input to this board - 5V is output from USB bus power.
do I need to connect pin 17 (3.3V)?
No, this is just the output from the on-chip FTDI 3V3 regulator.
what should I do with CTS and DTR pins? Can I just ground the through a resistor?
On Arduino, DTR is used by the auto-reset circuitry. DTR is connected to the AtMega reset pin along with a 100nF capacitor and a 10k pullup resistor. If you dont need it you can leave it unconnected along with the CTS pin.
finally... I assume I connect FTDI's TX (pin 1) to Arduino's RX (ATMega pin 2)?
Yes.
I'll be honets, buying it is too expensive, I'd rather do it.
The FTDI chip itself is quite expensive. If all you need is a low cost USB to TTL adapter, you can look for alternatives (down to 1US$) using other chips (e.g. Prolific based cables made for outdated cell-phones).
finally... I assume I connect FTDI's TX (pin 1) to Arduino's RX (ATMega pin 2)?
You'll need the RX pin connected to the Arduino's TX pin, too. The Arduino needs to be able to tell the computer that it is ready for a sketch to be uploaded.
There is no 5V input to this board - 5V is output from USB bus power.
So the pointing-up arrow with "5V" means only that it should be connected with "5V" wire at the power switch near the pins (on the right side of diagram)? Stupid me...
The FTDI chip itself is quite expensive. If all you need is a low cost USB to TTL adapter, you can look for alternatives (down to 1US$) using other chips (e.g. Prolific based cables made for outdated cell-phones).
How do I tell the cable is with adapter and not only the cellphone-side plug looks different, but it's the ordinary USB cable?
And what about drivers - with original Arduino with FTDI chip I had to have them installed. How to communicate with Arduino via that kind of cable?
You'll need the RX pin connected to the Arduino's TX pin, too. The Arduino needs to be able to tell the computer that it is ready for a sketch to be uploaded.
Yeah, I knew that, I just didn't want to repeat myself Also, I will need both, but only for transmission, I think I'll upload sketch with original board.
The FTDI chip itself is quite expensive. If all you need is a low cost USB to TTL adapter, you can look for alternatives (down to 1US$) using other chips (e.g. Prolific based cables made for outdated cell-phones).
Yes, I use PL2303HX as alternative. You can buy it on eBay.
This is the schematic.
PL2303HX is hard to get in Poland and as I can see, its price is similar to FT232 chip. So I'll think about FT232 or those cables BenF mentioned about, but I must read something more about it...
I converted two of those (PL2303 based) for use with custom Arduino's some time ago and they work just fine with drivers freely available for XP (and other platforms). I'm only using the internal circuit board with the mini-B USB connector. The PL chip is connected to a TTL-RS232 converter chip, but you can bypass this with wires for RX/TX soldered directly onto the PL2303 pins in addition to USB power and ground.
I never used the included CD, but downloaded the latest drivers from the Prolific web site. Apparently drivers are recently updated to also support 32 and 64 bit Widows 7.
The link is here:
If you know the USB chip used (there are really not that many around) you're typically better off getting the latest drivers from the manufacturers web-site.
