Read fail - size mismatch, will resync and continue

[20pyro00]

I don't know if i am doing something wrong, but when i try to do "Backup and flash new" or just "Firmware backup (read) only" i get a read fail. The program cycles through failed Sync attempts until it says "OK!" then says read fail again and it starts all over. I did everything as in "Detailed usage instructions (BK72xx)". What am i doing wrong?

[NonPIayerCharacter]

This usually means bad connection between adapter and chip.
Wires are too long?

[20pyro00]

The wires used are around 5cm long. I then tried another method like in this video: https://www.youtube.com/watch?v=bs0ylC6xRs0 . This worked, so i dont think it is a bad connection.

[mletenay]

I have exactly the same problem:

Now is: Friday, 27 March 2026 23:28:05.
Flasher mode: BL602
Going to open port: COM3.
Port ready!
Sync attempt 0/1000 ... OK!
BootROM version: 1 (1)
OTP flags:
00000000 00000000 00000000 00000000 
00000011 00000000 00000100 00000000 
01101001 01010000 01101100 11101101 
10111011 00101000 00011000 00000000 
Chip type: BL602

Sending boot header...
Sending segment header...
Writing application to RAM...
Checking...
Jumping...
Sync attempt 0/1000 ... OK!
Flash ID: C8401580
Flash size is 2MB
Starting read...
Reading at 0x000000... 
Read fail - size mismatch, will resync and continue
Sync attempt 0/1000 ... failed, will retry!
Sync attempt 1/1000 ... failed, will retry!
If doing something immediately after another operation, it might not sync for about half a minute
Otherwise, please pull high BOOT/IO8 and reset.
Sync attempt 2/1000 ... failed, will retry!
Sync attempt 3/1000 ... failed, will retry!
****