Without this fix Realforce 101 PS/2 fails to receive 'set indicator'
command sometimes when pressing Caps Lock and some keys simultaneously.
before fix:
____ ______
clock \___/
________
data \_______
| 100|
after fix:
____ __
clock \________/
________
data \_______
| 100| 100|
matrix_scan in hook_usb_startup_wait_loop is not required for
FC660C since commit dd7b75: SOF timing fix of USB_Host_Shield_2.0.
Without INTERRUPT_CONTROL_ENDPOINT the matrix_scan blocks around 2300ms
and prevents getting USB configured. In the result console_putc
starts sending before hid_listen is ready and chars are lost.
console_is_ready delay value should be around 5000ms if matrix_scan
is needed in hook_usb_startup_wait_loop.
The LUFA feature can prevent converter's ISR from handing signal instantly.
The interrupt can block a while for Standard Device Requests and 500-1000us
for keyboard LED report.
Because of integer promotion the compiler is having a hard time generating
efficient code to calculate TIMER_DIFF* macros in some situations.
In the below example, the return value is "int", and this is causing the
trouble.
Example C code:
int __attribute__ ((noinline)) test(uint8_t current_timer, uint8_t start_timer)
{
return TIMER_DIFF_8(current_timer, start_timer);
}
BEFORE: (with -Os)
00004c40 <test>:
4c40: 28 2f mov r18, r24
4c42: 30 e0 ldi r19, 0x00 ; 0
4c44: 46 2f mov r20, r22
4c46: 50 e0 ldi r21, 0x00 ; 0
4c48: 86 17 cp r24, r22
4c4a: 20 f0 brcs .+8 ; 0x4c54 <test+0x14>
4c4c: c9 01 movw r24, r18
4c4e: 84 1b sub r24, r20
4c50: 95 0b sbc r25, r21
4c52: 08 95 ret
4c54: c9 01 movw r24, r18
4c56: 84 1b sub r24, r20
4c58: 95 0b sbc r25, r21
4c5a: 93 95 inc r25
4c5c: 08 95 ret
AFTER: (with -Os)
00004c40 <test>:
4c40: 86 1b sub r24, r22
4c42: 90 e0 ldi r25, 0x00 ; 0
4c44: 08 95 ret
Note: the example is showing -Os but improvements can be seen at all optimization levels,
including -O0. We never use -O0, but I tested it to make sure that no extra code is
generated in that case.
