Myself and a colleague in work are developing a multiplexer that uses an ATMEGA328P-au as its controller. I can successfully burn the bootloader onto it, however, when i try to upload a sketch via usb it gives me the following errors:
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x79
I have checked the FTDI serial chip by performing a loop back test and it worked successfully so i do not believe that is the issue. i have also been able to program successfully using usbasp. And yes i am aware that doing this wipes the bootloader so that is not the issue. I always add the bootloader back before trying to program with USB.
I have attached my schematic. the only thing i can think of is the 20K resistor should be a 10k.
However even so, i can upload a hello world sketch via USBasp and still get no output on the serial monitor which makes me think there is something else going on.
Thanks for your help in advance!
Aref should not connect to +5. It should only have a cap to Gnd.
Pins 4, 6, and 18 should each have a cap.
The 20K might be too big, meaning Reset would stay low too long, or have too slow of a ramp up vs the ramp up that would occur with a 10K. Easy enough to try a fix - just put another 20K in parallel with it.
Also make sure you have nothing else hooked up to the tx and rx pins while programing
@CrossRoads would the 5V to AREF be causing this issue or is it just something that needs fixed on top of the serial problem?
I will definitely try and see if changing the resistor to 10K makes any difference.
@m_k_akash there are no other connections to tx or rx
also if rx and tx are working correctly should i not still be able to see outputs on the serial monitor if I upload a hello world sketch using USBasp?
oh i think i see the issue, are my TX and RX lines the wrong way round? i have tx to tx and rx to rx.
Can anyone please confirm?
Yes , indeed that's the problem tx should be connected to rx and rx should be connected to tx . All the best
fantastic that should be easy to fix. Will update when its fixed!
jumping the rx to tx and tx to rx worked a treat! Thanks for your help
Happy to hear the good news !!