arduinoftdireset
How do you get the SparkFun FTDI Basic Breakout board to auto reset?
I still have to hit the reset button for any Arduino clones when I use the breakout board. I have tried connecting to the DTR pin and other methods of trial and error but I am just not getting it.
As Joby Taffey suggests, the rx & tx pins of the AVR are 2 & 3 respectively, but on the Arduino headers they are pins 0 & 1. You also want to connect DTR to the reset pin of the arduino to enable automatic programming.
FTDI Arduino
Breakout (5V)
GND <--> GND
CTS <--> (not connected)
5V <--> 5V (if you want the breakout to power the arduino)
TXO <--> RX (pin 0)
RXO <--> TX (pin 1)
DTR <--> RESET (possibly through a 100nF cap*)
On the FTDI TTL232R cable, DTR is not present so you have to manually reset the board before flashing. By default the Arduino will stay in the bootloader for 6-8s, but some boards rely on the automatic reset and have much shorter timeouts (0.25s say). For these boards, set upload.verbose = true in your Arduino conf file, and learn to time the reset the moment the software attempts to flash the board.
IIRC the cap is wired to /RTS not DTR.
When /RTS is high there is 0V across the cap. When /RTS goes low the cap can not change voltage instantaneously so the reset line goes low. The cap charges through the 10K resistor. Once the reset line is above the reset threshold the uC program starts.
@LouisDavis referenced this page, which states
The ATmega168 is reset by pulsing its reset pin to GND. ...by setting the DTR line to LOW ... the reset pin gets sucked to LOW until the capacitor is charged through the internal pull up resistor and R1 - which resets the chip.
Simulated:
Auto-Reset
VDTR 1 0 PWL(0 5 0.5m 5 0.000500004 0 1m 0)
Vcc 3 0 5
C1 1 2 100n
R1 3 2 10k
.control
delete all
tran 10n 5m
plot v(1) v(2)
.endc
.END
V(1) is DTR or /RTS and V(2) is /RESET
Best Answer
What I did to get my breadboard arduino to reset was to go into the device manager (Windows 7) and highlighted the FTDI device (A virtual COM port) and then went to Properties, Port settings, Advanced. I then checked off the box that said "Set Rts on close". After I did this my arduino reset itself no problem. Hope this helps.