XMODEM File Transfer

Packet:

┌─────────┬────────┬──────────┬───────────┬──────────┐
│ SOH     │ Packet │ Inverted │ Data      │ Checksum │
│ 0x01    │ Number │ Number   │           │          │
├─────────┼────────┼──────────┼───────────┼──────────┤
│ 1 byte  │ 1 byte │ 1 byte   │ 128 bytes │ 1 byte   │
└─────────┴────────┴──────────┴───────────┴──────────┘

- Start with NAK 0x15 to initiate protocol. 
- After each packet followed with ACK 0x06 when received or NAK 0x15 if not.  
- Wait 10 seconds and retry 10 times. 
- After last packet send EOT 0x04