zx-328n start up

[rdrive]

I was wondering if pin 1 and 3 have to be pulled up to operate. I have already programmed it but I'm using it in another board without programming inputs and it won't start. is my pull ups the problem?

[kranenborg]

Hello,

The manual mentions that at least pin 3 (TX) needs to be pulled high, pin 1 is already internally pulled high. On my programming board for the ZX-328 I have only pulled pin 3 high, and this always works! I can imagine that this is the issue in your case, and it can be easily checked I guess.

Best regards,
Jurjen

[dkinzer]

I was wondering if pin 1 and 3 have to be pulled up to operate.

Although the mega328P chip does have internal pullups, they are fairly weak. That is why we recommend using a lower value external pullup. The only disadvantage is that the lower resistance pullup resistors do increase the power consumption slightly but only when the particular lines are pulled low.

If the device worked correctly in the circuit that you used to program it but it does not work in a different circuit it is logical to conclude that there is some difference that is preventing it from working. You might consider constructing an alternate circuit on a breadboard that is identical to the programming circuit and then methodically remove unneeded parts one at a time, confirming that it still works at each step.

[rdrive]

Thank you both very much I did put in the pull ups but it still didn't start but I'm sure I'll find a wiring error.
Thanks again

[rosariote]

Hi,
Pin 1 it is the RESET pin and it need to be high. I used a 10k pull up resistor. When the pin it is grounded it will reset the micro.

[DocJC]

Although many add an external pull up resistor on the Reset\ pin, I doubt that is the reason the OP's circuit is not working.

The Mega AVR's have an internal pull up resistor on the Reset\ pin by default.

JC