avr: cleanup lowlevel com2 routines.

avr/modules/com2/lowlevel.asm

@@ -81,20 +81,20 @@ com2ReceiveByte:
   ldi r21, 8                                   ; bits left
   clr r20                                      ; byte currently receiving
   ; wait for startbit
-  rcall com2WaitForDataLow                      ; (R17)
+  rcall com2WaitForDataLow                     ; (R16, R17, R22)
   brcc com2ReceiveByte_error
   Utils_WaitNanoSecs COM_BIT_LENGTH/2, 5, r22  ; goto middle of startbit to maximize sync stability
 com2ReceiveByte_loop:
     Utils_WaitNanoSecs COM_BIT_LENGTH, 8, r22  ; 8 cycles used in the complete loop between waits
     sec                                        ; +1
     sbic COM_PIN_DATA, COM_PINNUM_DATA         ; LOW: +2, HIGH: +1
-      rjmp com2ReceiveByte_shiftIn              ; HIGH: +2, rjmp, use set CFLAG
+      rjmp com2ReceiveByte_shiftIn             ; HIGH: +2, rjmp, use set CFLAG
     clc                                        ; LOW: +1
 com2ReceiveByte_shiftIn:
     ror r20                                    ; +1
     dec r21                                    ; +1
-  brne com2ReceiveByte_loop                     ; +2, sum per loop: 8 cycles
-  rcall com2WaitForDataHigh                     ; wait for start of stopbit
+  brne com2ReceiveByte_loop                    ; +2, sum per loop: 8 cycles
+  rcall com2WaitForDataHigh                    ; wait for start of stopbit
   brcc com2ReceiveByte_error
   mov r16, r20
   sec
@@ -112,23 +112,11 @@ com2ReceiveByte_error:
 ; IN:
 ; OUT:
 ; - CFLAG: set if okay, clear otherwise
-; MODIFIED REGISTERS: r17, r22
+; MODIFIED REGISTERS: r16 (r17, r22)
 
 com2WaitForDataLow:
-  ldi r17, COM2_MAXWAIT_US
-
-com2WaitForDataLow_loop:
-    sbis COM_PIN_DATA, COM_PINNUM_DATA
-      rjmp com2WaitForDataLow_done
-    rcall com2WaitFor1000ns
-    dec r17
-  brne com2WaitForDataLow_loop
-  clc   ; timeout
-  ret
-
-com2WaitForDataLow_done:
-  sec   ; ok
-  ret
+  clr r16
+  rjmp com2WaitForDataState1ms
 
 
 
@@ -139,23 +127,11 @@ com2WaitForDataLow_done:
 ; IN:
 ; OUT:
 ; - CFLAG: set if okay, clear otherwise
-; MODIFIED REGISTERS: r17, r22, X
+; MODIFIED REGISTERS: r16 (r17, r22)
 
 com2WaitForDataHigh:
-  ldi r17, COM2_MAXWAIT_US
-
-com2WaitForDataHigh_loop:
-    sbic COM_PIN_DATA, COM_PINNUM_DATA
-      rjmp com2WaitForDataHigh_done
-    rcall com2WaitFor1000ns
-    dec r17
-  brne com2WaitForDataHigh_loop
-  clc   ; timeout
-  ret
-
-com2WaitForDataHigh_done:
-  sec   ; ok
-  ret
+  ldi r16, 0xff
+  rjmp com2WaitForDataState1ms
 
 
 
@@ -166,23 +142,11 @@ com2WaitForDataHigh_done:
 ; IN:
 ; OUT:
 ; - CFLAG: set if okay, clear otherwise
-; MODIFIED REGISTERS: r17, r22, X
+; REGS: r16 (r17, r22)
 
 com2WaitForAttnHigh:
-  ldi r17, COM2_MAXWAIT_US
-
-com2WaitForAttnHigh_loop:
-    sbic COM_PIN_ATTN, COM_PINNUM_ATTN
-      rjmp com2WaitForAttnHigh_done
-    rcall com2WaitFor1000ns
-    dec r17
-  brne com2WaitForAttnHigh_loop
-  clc   ; timeout
-  ret
-
-com2WaitForAttnHigh_done:
-  sec   ; ok
-  ret
+  ldi r16, 0xff
+  rjmp com2WaitForAttnState1ms
 
 
 
@@ -215,18 +179,30 @@ com2WaitForDataState1ms_stateReached:
 
 
 ; ---------------------------------------------------------------------------
-; comWaitFor1000ns
+; com2WaitForAttnState1ms
 ;
-; Waits for 1000 nanoseconds.
+; Waits up to 100ms for high DATA line
 ; IN:
+; - R16: state to wait for (00 for low, 0xff for high)
 ; OUT:
-; - CFLAG: set if okay, clear otherwise
-; REGS: r22
-
-com2WaitFor1000ns:
-    Utils_WaitNanoSecs 1000, 7, r22 ; wait for 1000 nanosecs (minus 3 cycles for rcall, 4 for ret)
-    ret
+; - CFLAG: set if state reached, cleared otherwise
+; REGS: R17, R22
 
+com2WaitForAttnState1ms:
+  ldi r17, 100
+com2WaitForAttnState1ms_loop:
+    in r22, COM_PIN_ATTN
+    eor r22, r16
+    andi r22, (1<<COM_PINNUM_ATTN)
+    breq com2WaitForAttnState1ms_stateReached
+    Utils_WaitNanoSecs 10000, 0, r22              ; wait for 10us
+    dec r17
+  brne com2WaitForAttnState1ms_loop
+  clc
+  ret
+com2WaitForAttnState1ms_stateReached:
+  sec
+  ret