Dan,
This inter-byte delay timing is rather unfortunate. I assume your testing shows that this is the only way the radio will accept the image?
For testing here I have used a Windows 7 64-bit PC, a Linux Mint 64-bit PC and a Windows 10 32-bit virtual machine. On every one of these machines, I can send the upload to the radio at full speed. smb://tower/disk2/Drivers,%20Manuals%20&%20Firmware/RETEVIS/RT23/RT23_Write_Factory.txt
I have had 2 testers tell me that they cannot upload to their respective radios without this hack. Both tell me that the factory software uploads to their radio just fine.
I don't like doing it this way either. Unfortunately, I'm not sure I have what it take to figure it out. But I sure would like to figure it out. Because I would like to get rid of it on the btech.py driver as well.
I have attached the serial port capture that I made using Windows 7 and my RT23. Does it provide a clue as to how I can resolve this. I know about Retevis, but if this can be resolved in a reasonable amount of time, I would rather delay adding this go CHIRP. I just need to assistance/advice on how to proceed.
Have you tried doing something like writing 8 bytes at a time, with a sleep in between or something like that?
I will give this a try.
Thanks, Jim