I have built a stand alone system with the ATMEGA 2560 and I have used an Arduino ATMEGA2560 as ISP to program my ATMEGA 2560 with a bootloader. This worked well and I can use a FTDI to RS232 converter along with a RS232 to TTL converter to upload sketches. I just connect +5v,Tx,Rx,GND and push my reset button and it works. I then bought an arduino USB 2 serial converter and hooked up +5v,Tx,Rx,GND and pushed my reset button and it does NOT work. I tested the USB 2 serial converter by tying Tx to Rx and I can see it echo characters. So my question is has anyone successfully used the USB 2 serial converter to upload sketches to an ATMEG 2560 ?
one other thing when I use the USB 2 Serial converter I can see my standalone ATMEGA2560 output info from a sketch I loaded using the FTDI to RS232 cable.
On the Arduino page for the usb 2 serial converter it mentions
The adapter can easily connect to the Arduino Ethernet, Mini, Mini Pro, LilyPad, LilyPad Simple, and Fio.
I am wondering if it is too slow for the ATMEGA 2560
on the USB 2 serial converter I see both the TX and RX leds light up. Since I can see text from a previous sketch appear on the ARDUINO IDE serial monitor I am pretty sure I have the RX and TX hooked up correctly. I did reverse them and I still cannot get a sketch to upload.
Mega2560 runs at the same 16 MHz as all the other parts you mentioned. Post your 2560 schematic, maybe you're missing something in the reset circuit, like a 10K pullup, 0.1uF DTR cap, diode with anode to +5 to stop any spikes on the reset line from triggering the chip into high voltage programming mode and looking hung until it is reset.
my full schematic is five pages long. I have attached the reset section.
my FTDI USB to RS232 through a RS232 to TTL adaptor works if I ground TP101 and then release it as the IDE starts with program uploading.
thanks
Phil
Design looks ok.
Try File:Preferences, turn on verbose outputs.
Press & Hold Reset (TP101), when the IDE shows "compiled xxx bytes of 128xxx bytes" release Reset. Can be easier to get the timing of the release that way.
okay I will try that tomorrow. By the way I have the arduino/ Genuino Mega or Mega2560
as the board selection in the IDE.
well I tried releasing the ground on TP101 as the IDE reported the "compiled xxx bytes of 128xxx bytes" and that did not work. I noticed each time I release the ground on TP101 the TX led flashes but the RX led does not flash. I tested my usb to micro usb cable on a DUE and it loaded code successfully.
I went to the send block on the serial monitor and when I put in some characters and hit send the RX led flashes.
When my program powers up I see the header that prints on the serial monitor screen.
I crossed the RX and TX leads and when I hit send on the serial monitor the string is echoed on the screen.
I think I have it wired correctly and the parts are all working.
I was wondering if anyone else has tried this and got it to work.
well I got it to work. The Arduino store said I had to connect the USB 2 serial converter reset line to my TP101 (atmega2560 reset pin) with a 10 uf cap. I did this and it worked !!!!
so problem solved. The USB 2 serial converter documentation does not mention this as far as I can tell.
well the documentation does say a 100nf cap. I tried that and it did not work so the larger 10 uf cap is needed.
on the ATMEGA2560 product schematic there is a 100 nf cap. But my standalone design with its five page schematic has more stuff attached to the reset line than just the ATMEGA2560 cpu. so I am guessing that is why I need to use a larger cap.
