Can't upload via FTDI to atmega328pb

I have a bespoke board that looks to the outside world like some Uno clones (it uses the FT232RL FTDI chip), but it uses the Atmega328PB rather than the Atmega328P. I amended the expected signature for the Atmega328P in avrdude.conf to match the signature of the Atmega328PB.

Results are as follows

I can burn the Atmega328P bootloader through the interface using the Arduino.org ISP and the latest IDE. This appears to go through without error.

Similarly, I can upload a simple sketch using the "Upload using Programmer" option

This sketch returns Serial data correctly to the Serial monitor

BUT I cannot upload sketches direct from the IDE to the board in the normal way. I get "stk500_getsync()..." errors. I have tried several suggestions for fuse settings found on the web, and they result in different response codes

I don't need the extra facilities in the Atmega328PB - happy to have it behave as an Atmega328P

Any suggestions for fixing the problem?

When you do "Upload Using Programmer" it erases the bootloader. That means you will no longer be able to do an upload over serial using your FTDI chip. After doing Upload Using Programmer you need to do Tools > Burn Bootloader before you can start uploading over serial again.

pert:
When you do "Upload Using Programmer" it erases the bootloader. That means you will no longer be able to do an upload over serial using your FTDI chip. After doing Upload Using Programmer you need to do Tools > Burn Bootloader before you can start uploading over serial again.

Many thanks for that. It isn't the core issue in this case but I wasn't aware of this

That seems strange. Do you have details on the board you are using? One possibility is that the board (and core) use the NEW uart for upload, and the bootloader is still using the original uart.

Is the board clocked at the speed the bootloader was built for?

A couple of useful thoughts here:

Here is the fragment of schematic for the micro:

I'm using a 16 Mhz oscillator

Many thanks

Your schematic shows a 328p, not a 328pb… they don’t have quite the same pinout (I think you should be able to put a 328pb on a 328p board, as long as you don’t set any of the new gpio pins that used to be power pins to “output.”)

So you’re also using the standard “Uno” core, rather than a special 328pb core?

westfw:
Your schematic shows a 328p, not a 328pb... they don't have quite the same pinout (I think you should be able to put a 328pb on a 328p board, as long as you don't set any of the new gpio pins that used to be power pins to "output.")

So you're also using the standard "Uno" core, rather than a special 328pb core?

Yes you are quite right. Right footprint, wrong part. Doh. Apologies for wasting everyon's time

(mind you, I don't think that this explains the behavior you're seeing!)

westfw:
(mind you, I don't think that this explains the behavior you're seeing!)

Yes that is odd. I might persevere and correct it in the next iteration (this is the very first prototype board). Many thanks for your help.