seperate ATmega 2560 - turn on a single LED - troubleshooting

Question

I have got my own PCB with "some stuff" on it and first I want to make it run a simple "turn on LED".

My setup:

• Atmega 2560
• LED connected to PE4 (D2 in Arduino language) => PE4 - LED - 1K resistor - 5V
• ceramic resonator (CSTCE16M0V53-R0 16MHZ) connected to XTAL1 + XTAL2 with 1MOhm resistor inbetween
• all VINs are pulled to GND with capacitors

Upload is working through ICSP (MISO, MOSI, SCK, RESET, 5V, GND) with an USBasp

Here is my Arduino sketch, which I upload through the Arduino software:

void setup() {
  pinMode(2, OUTPUT);
}

void loop() {
  digitalWrite(2, LOW);    
}

I checked the fuses on the atmega as well:

avrdude: safemode: lfuse reads as FF
avrdude: safemode: hfuse reads as D8
avrdude: safemode: efuse reads as FD
avrdude: safemode: Fuses OK (H:FD, E:D8, L:FF)

avrdude uploads successfully: (output truncated!)

avrdude: auto set sck period (because given equals null)
avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.01s
avrdude: Device signature = 0x1e9801
avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed
         To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: auto set sck period (because given equals null)
avrdude: writing flash (1518 bytes):
Writing | ################################################## | 100% 5.47s
avrdude: 1518 bytes of flash written
avrdude: reading on-chip flash data:
Reading | ################################################## | 100% 3.45s
avrdude: verifying ...
avrdude: 1518 bytes of flash verified

avrdude done.  Thank you.

Problem: the LED doesn't work. It is OFF all the time.

Any ideas why it is not working?

Cheers Hendrik

Answer 1

You are saying that the LED lights if you write LOW to it.

I need to pull the output pin to LOW to make the LED work

That's exactly what you expect.

Since the other end of the LED is wired to +5 V, then you need to drive the pin low to have a voltage difference over the LED, and for it to light.

---

I double checked the Atmega and it is a ATmega2560V, which is rated for 8Mhz. Any chance to fix this with the existing PCB? Change the Fuses to use the internal clock?

Yes, I suggest you do that.

Look at Engbedded Atmel AVR® Fuse Calculator to see what to set them to. I suggest the internal 8 MHz oscillator.