[FEATURE REQUEST]BTT Fast Upload support

[luc-github]

Now MKS (TFT and board) fast upload is implemented what about BTT TFT and board ?

MKS protocol use 2 pins GPIO0 and GPIO4 with ESP12

BTT use ESP01 port which has GPIO0 and GPIO2
BTT TFT only connect GPIO0 https://github.com/bigtreetech/BIGTREETECH-TFT35-V3.0/blob/master/Hardware/TFT35%20V3.0-PIN.pdf
BTT SKR Pro seems connect all pins https://github.com/bigtreetech/BIGTREETECH-SKR-PRO-V1.1/blob/master/Schematic/SKR-PRO-V1.1%EF%BC%88SCH%EF%BC%89.pdf
BTT GTR only connect GPIO0 https://github.com/bigtreetech/BIGTREETECH-GTR-V1.0/blob/master/BTT%20GTR%20V1.0/manual/GTR%20V1.0(SCH).PDF

So we cannot just use the MKS protocol as it is

Also any implementation will need in addition of ESP3D update

• BTT TFT FW update for BTT TFT
• Marlin FW update for SKR and GTR

the 2 pins usage are :

• one pin to request to Main board to allow to send data - managed by ESP board
• one pin to inform ESP the data can be send - managed by printer/tft board

This allow an hardware ping/pong to send packets
Also be noted MKS protocol only allows text files not binaries files due to usage of flags 0xa5 (HEAD) and 0xfc (TAIL) which could be present in a binary file, and there is no integrity check - just data quantity check per fragment defined by HEAD and TAIL, in between, data can be corrupted - there is no check - but this is not the subject of this tread

So need another protocol - TBD
One simple solution would be to use a command from ESP to request Board send data (initiate) and use the only pin to notify esp it can/cannot send data, the information in each packet is normaly enough to know what is going on

[luc-github]

need to do some POC to check transfer speed but this could be a solution : https://github.com/PowerBroker2/SerialTransfer