Optimization notes

[ConsciousCode]

These are notes I made during work for how the code could be improved:

• Add a new mode for monitoring the CEC bus (ie read all messages into the buffer to be read back to the i2c master)
• In command processing, a few opcodes can be saved (and flow made more intuitive) by adding an i2c_ignore_rest label with ldi state, IDLE DONE
• Eventually: Use the remaining registers to hold constants to condense the ldi tmp, CONST op reg tmp pattern into a single op (eg enable_timer would benefit). Already have zero_reg which we can be assured can't be non-zero in normal program operation
• May be possible to condense reading/writing into the buffer into a subroutine and actually use the stack, since in either mode they use the same registers
• grep "sanity check" - forgot to comment an if-else pair, among a few other things
• cec_notpoll - why are we processing EOM when we don't know if it's for us? Need to move the address check up a few blocks
• In PCINT0, OLD_CEC^OLD_SDA = 1, we should be able to adjust gbf with an and and eor
• Add note to readme about how the second HDMI cable can be used as a programming interface even if the wires were badly cut
• Set the timer overflow interrupt to ensure that it never overflows and retriggers the compa interrupt - overflow only takes like 8 seconds
• It should be possible to use the RESET/Pin 3 as a UART debug output if we count cpu cycles. This may give something to put in the rest of the program memory (debug messages)!
• I've totally ignored the cpse instruction, there may be some places in the code where it saves an opcode
• ijmp and icall should be carefully considered as possibilities for enabling extremely common global branches.
• Forgot to apply memory mapping for indirect addressing, SRAM begins at 0x0040, not 0x0000. lds and sts are OK because they implicitly add 0x0040