Strange issues burning a bootloader into a TQFP 328P-AU

Hi all!
I’m using an old Arduino (Pro 168 & 16Mhz) like ISP programming device.
I always use it to burn Pro 168 and 328 with any problem (DIP).

Now I’m using it to burn a few TQFP 328 P-AU.
The programming task goes great, i mean the blank chip is erased and burned with the PRO bootloader.

But using this new arduino I noted some issues at the SPI port (resets the uP), so doing some debugging procedures I discover that is a short circuit.

For some reason if I set the SCK port this issue appears, is like a short circuit inside the uP.

The last trick that I get is use this new TQFP Arduino as ISP. To program others uP. This trick do not give me any result I can use the new Arduino as ISP.

The last idea that i get is use the parallel port to burn directly this blanck TQFP part and then load the ISP sketch on it to get a TQFP Arduino ISP.

So let me know if my procedures are correct, or if I’m missing some thing.

Best Regards

The ATmega328P has probably the same chip inside every package (PDIP, TQFP, MLF).
There should be no difference.
The DIP ATmega328P has even the A6 and A7, but they are inside, they just have no wire to the outside.

Can you try a normal DIP ATmega328P, to check for anything odd ?
Did you connect the GND and power pins of the TQFP correctly ? It is best to connect all GND pins to GND and all VCC and also AVCC to 5V.

[ADDED] Read the word “best” as “mandatory” :wink: DrAzzy is right of course in Reply #2.

What issues? What does "set the SCK port" mean? "you discover that it is a short circuit"? What is shorted to what?

If there is a short, it is either on the PCB (so fix it), a bad soldering job (so fix it) or the chip is damaged or defective (throw it out).

It sounds like this is a custom PCB - did you forget the decoupling capacitors? There must be 3 0.1uf caps, one for each vcc pin, plus one for avcc, located as close to the chip as possible

Peter_n - it is not just "best" to make those connections to the gnd and vcc/avcc pins. It is required for proper functioning - not doing so is wrong. A disturbing number of tutorials omit the decoupling caps, and sometimes even the connection between AVcc and Vcc (note - you get best ADC readings by connecting Vcc to AVcc through a low pass filter, as recommended by the datasheet - but hardly anyone does that, not even the official arduino boards; the ADC readings are "good enough" with AVcc directly connected to Vcc. But they must be connected, otherwise some parts of the chip are being powered only by the grace of a protection diode, which is likely being pushed out of spec)

Yup, don’t forget the caps and reset pullup resistor per the attached. Diode across the pullup resistor prevents the chip from being hung in high voltage programming mode too when a reset switch is used.

AtmelAVR042 AVR Design Considerations.pdf (236 KB)