diff options
| -rw-r--r-- | converter/adb_usb/matrix.c | 20 |
1 files changed, 17 insertions, 3 deletions
diff --git a/converter/adb_usb/matrix.c b/converter/adb_usb/matrix.c index d1b67d38d6..405391865f 100644 --- a/converter/adb_usb/matrix.c +++ b/converter/adb_usb/matrix.c @@ -88,12 +88,26 @@ void matrix_init(void) uint8_t matrix_scan(void) { + /* extra_key is volatile and more convoluted than necessary because gcc refused + to generate valid code otherwise. Making extra_key uint8_t and constructing codes + here via codes = extra_key<<8 | 0xFF; would consistently fail to even LOAD + extra_key from memory, and leave garbage in the high byte of codes. I tried + dozens of code variations and it kept generating broken assembly output. So + beware if attempting to make extra_key code more logical and efficient. */ + static volatile uint16_t extra_key = 0xFFFF; uint16_t codes; uint8_t key0, key1; is_modified = false; - _delay_ms(12); // delay for preventing overload of poor ADB keyboard controller - codes = adb_host_kbd_recv(); + + codes = extra_key; + extra_key = 0xFFFF; + + if ( codes == 0xFFFF ) + { + _delay_ms(12); // delay for preventing overload of poor ADB keyboard controller + codes = adb_host_kbd_recv(); + } key0 = codes>>8; key1 = codes&0xFF; @@ -113,7 +127,7 @@ uint8_t matrix_scan(void) } else { register_key(key0); if (key1 != 0xFF) // key1 is 0xFF when no second key. - register_key(key1); + extra_key = key1<<8 | 0xFF; // process in a separate call } return 1; |