Arduino Mega 2560 on pcb

Using Arduino Microcontrollers
1

I have made a PCB with ATmega2560 controller. I am using a 16MHz crystal with two 22pF capacitors . Each attached to one of the crystal pin and the other to ground. I have also attached a 1K resistor between reset and VCC pin of controller. I have soldered already programmed ic for blinking leds. It is working. But I want to upload the code using USB-to-TTL. I tried many different ways which includes:

  • pressing the reset button (between GND and RESET pins) till the uploads starts.

  • using a 0.1uF capacitor in the RESET and DTR pin of another Usb-to-ttl converter

  • used another arduino to upload the code

But nothing worked. Kindly help me out if I am missing any important component on the PCB. Or what can I do to upload the code? What could be the problem? A good schematic for ATmega controller would also be appreciated. The schematic I found on the official site didn't worked for me too.

2

Share the schematic of your design with us.

Was this IC programmed directly with the blinking LED sketch or via an already programmed in bootloader?

The chip needs a bootloader programmed into it and the appropriate fuses set in order to do this. You also need to know which of the 4 serial ports has been designated for the bootloader to use.

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In your chematic you missed line 42.

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Share the schematic of your design with us.

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This is the schematic design.

The IC was programmed with the blinking leds code at different number of pins. It was programmed when the IC is on Arduino Mega board. I programmed it it then just de soldered it. It was working on my designed pcb. The problem is now uploading on my pcb.

I am using RX0 and TX0 of the controller connected to TX and RX of usb to ttl.

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If the chip doesn't have a bootloader, you won't be able to upload code. To upload a bootloader, you need to breakout SPI and upload the bootloader using Arduino as ISP

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Sorry I didn't get you. Can you point me more clearly what you want to say. Thank you

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It has a bootloader on it. I have told in my post that I have desoldered the IC from a working Arduino Mega Board. And now i want to upload the code using usb-to-ttl.

1 Like
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What USB to TTL module are you using?

10

I have tried two usb to ttl modules.

  • FT232RL FTDI with a DTR pin
  • CP2102
    I have also tried another arduino as ISP. But nothing worked for me.
11

I don't see the traditional 6-pin ICSP header or 6-pin FTDI header.

Your design is missing decoupling capacitors and the reset circuit is incomplete.

For a minimal MEGA2560 design, have a look at the reference design at the bottom of the MegaCore github page.

1 Like
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Thank you @markd833 . I will try this solution you gave. It seems helpful.

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My schematic worked. Thankyou you all for your help. There was a little fault in soldering. Which i accidently found.Glad you all helped.

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