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-rw-r--r--converter/adb_usb/matrix.c20
1 files changed, 17 insertions, 3 deletions
diff --git a/converter/adb_usb/matrix.c b/converter/adb_usb/matrix.c
index d1b67d38d..405391865 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;