Merge branch 'rhaberkorn-serial-mouse'

[tmk_firmware.git] / protocol / ps2_busywait.c

diff --git a/protocol/ps2_busywait.c b/protocol/ps2_busywait.c
index 5ab377877ec9a0e3e4e9046f00f03e68c81214a7..05dd7b27e695762cb50e0befadc60395e6a1ca3f 100644 (file)
--- a/protocol/ps2_busywait.c
+++ b/protocol/ps2_busywait.c
@@ -35,16 +35,16 @@ ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 POSSIBILITY OF SUCH DAMAGE.
 */
 
+/*
+ * PS/2 protocol busywait version
+ */
+
 #include <stdbool.h>
 #include <util/delay.h>
 #include "ps2.h"
 #include "debug.h"
 
 
-/*
- * PS/2 protocol busywait version
- */
-
 #define WAIT(stat, us, err) do { \
     if (!wait_##stat(us)) { \
         ps2_error = err; \
@@ -52,6 +52,7 @@ POSSIBILITY OF SUCH DAMAGE.
     } \
 } while (0)
 
+
 uint8_t ps2_error = PS2_ERR_NONE;
 
 
@@ -65,18 +66,19 @@ void ps2_host_init(void)
 
 uint8_t ps2_host_send(uint8_t data)
 {
-    uint8_t res = 0;
     bool parity = true;
     ps2_error = PS2_ERR_NONE;
+
     /* terminate a transmission if we have */
     inhibit();
-    _delay_us(200); // at least 100us
+    _delay_us(100); // 100us [4]p.13, [5]p.50
 
-    /* start bit [1] */
+    /* 'Request to Send' and Start bit */
     data_lo();
     clock_hi();
-    WAIT(clock_lo, 20000, 10);   // may take 15ms at most until device starts clocking
-    /* data [2-9] */
+    WAIT(clock_lo, 10000, 10);   // 10ms [5]p.50
+
+    /* Data bit */
     for (uint8_t i = 0; i < 8; i++) {
         _delay_us(15);
         if (data&(1<<i)) {
@@ -88,15 +90,18 @@ uint8_t ps2_host_send(uint8_t data)
         WAIT(clock_hi, 50, 2);
         WAIT(clock_lo, 50, 3);
     }
-    /* parity [10] */
+
+    /* Parity bit */
     _delay_us(15);
     if (parity) { data_hi(); } else { data_lo(); }
     WAIT(clock_hi, 50, 4);
     WAIT(clock_lo, 50, 5);
-    /* stop bit [11] */
+
+    /* Stop bit */
     _delay_us(15);
     data_hi();
-    /* ack [12] */
+
+    /* Ack */
     WAIT(data_lo, 50, 6);
     WAIT(clock_lo, 50, 7);
 
@@ -105,17 +110,16 @@ uint8_t ps2_host_send(uint8_t data)
     WAIT(data_hi, 50, 9);
 
     inhibit();
-    res = ps2_host_recv_response();
+    return ps2_host_recv_response();
 ERROR:
     inhibit();
-    return res;
+    return 0;
 }
 
 /* receive data when host want else inhibit communication */
 uint8_t ps2_host_recv_response(void)
 {
-    // Command might take 20ms to response([3]p.21)
-    // TrackPoint might take 25ms ([5]2.7)
+    // Command may take 25ms/20ms at most([5]p.46, [3]p.21)
     // 250 * 100us(wait for start bit in ps2_host_recv)
     uint8_t data = 0;
     uint8_t try = 250;
@@ -125,14 +129,6 @@ uint8_t ps2_host_recv_response(void)
     return data;
 }
 
-/* send LED state to keyboard */
-void ps2_host_set_led(uint8_t led)
-{
-    ps2_host_send(0xED);
-    ps2_host_send(led);
-}
-
-
 /* called after start bit comes */
 uint8_t ps2_host_recv(void)
 {
@@ -180,3 +176,10 @@ ERROR:
     inhibit();
     return 0;
 }
+
+/* send LED state to keyboard */
+void ps2_host_set_led(uint8_t led)
+{
+    ps2_host_send(0xED);
+    ps2_host_send(led);
+}