series description 1. GPI02, GPI00 and MTD0 are used to select the startup mode and SD10 mode; for GP100 download mode: external pull-down, run mode: suspend or external pull-up; 2. UOTXD should be avoided to be externally pulled down to a low level during the power-up period. 3.UARTO will output printing during power-on startup by default, the baud rate of the printed content during this period is related to the frequency of the crystal used. When using 40MHz crystal, the baud rate of this section is 115200; when using 26MHz crystal, the baud rate of this section is 74880. If the print information affects the function of the device, it is recommended that UOTXD and UORXD be exchanged during the power-up period with UORTS(MTDO) and UOCTS(MTCK) respectively to shield the print; 4 where GPI00 connects to the download module, it should avoid being pulled down externally; 3. 4. where GPI00 connects to the B00T pin of the download module.