Execution time of the "Clear display" command is not specified
in the HITACHI date sheet HD44780U, page 24. (Probably a misprint)
It was measured and found to be 1.6 to 2.4 ms +- 0.2 ms
2.6 ms delay after LCD_RETURNHOME
*
Execution time of the "Return home" command is specified as 1.52 ms
in the HITACHI date sheet HD44780U, page 24. (Probably meant for
"Clear display")
It was measured and found to be less than 0.8 ms and is probably
37 us like all other commands. To be safe the delay was added here
also as it hardly influences performance.
change SEQOP_ON to SEQOP_OFF in piface_open_noinit()
These values set bit 5 of the IOCON register in the MCP23S17 I/O Expander. Setting this bit to 0 (SEQOP_ON) enables address pointer increments in the MCP23S17. I do not think this is ever used (especially with BANK_OFF). Every command to the MCP23S17 sets a new address. The auto-incrementing of text byte transfers in the HD44780U is handled somewhere else.
change SEQOP_ON to SEQOP_OFF in piface_open_noinit()
These values set bit 5 of the IOCON register in the MCP23S17 I/O Expander. Setting this bit to 0 (SEQOP_ON) enables address pointer increments in the MCP23S17. I do not think this is ever used (especially with BANK_OFF). Every command to the MCP23S17 sets a new address. The auto-incrementing of text byte transfers in the HD44780U is handled somewhere else.