; KeyScan.spt   -  Key scan function.
**********  Start of test code ***********************
*********** You can safely delete the test code once ***************** 
*********** you are familiar with the function       *****************
		OBLCD_Cls
		STScale		1
		LaunchTask	KPD_Start
		LaunchTask	Test

		RunTasksForever


Test:
		YieldTask
		GoSub		KPD_GET_Key
		GoIfF		Test

		OBLCD_SetCur	0,0
		OBLCD_HexDispX
		GoTo		Test

********** End of test code ***************************




;======= Key pad ===================
;Short name	KPD_

;Entry points:
;		Start		;The task to launch
;		GET_Key		;Get any result.
;				;Returns X = T if there is a key stroke
;				;	 Y=Key code
;				;A key is returned with X=T only once.

;Size: 207 bytes Flash. 3 bytes and 1 bit of RAM

;The code returned is a function of row and column, generated by a
;table in NVEM.

;A 4x4 keypad is connected to 4 outputs (rows) and 4 inputs (columns)
;Note that whether outputs are rows or columns is an arbitrary hardware design
;decision. We have made one choice in this program. "Unscrambling" is a matter
;of updating the translation table

oKPD_Rows	oEQU		0	;Base address of row outputs
iKPD_Cols	iEQU		0	;Base address of column inputs

KPD_Row:	defByte
KPD_Col:	defBYTE
KPD_Temp:	defBYTE
sKPD_Flag:	defSEM

KPD_Start:
KPD_Set0:
		LoadX		'F
		Push
		OutputM		oKPD_Rows	;Turn on all row drives
KPD_Set0a:
		MarkTime
KPD_0:	;Wait for all inputs off for at least 50mS
		YieldTask
		InputFM		iKPD_Cols
		LoadX		'F
		AndM
		GoIfNZ		KPD_Set0a
		LoopIfTiming	5,KPD_0
KPD_Set1:
KPD_1:	;Wait for any input
		YieldTask
		InputFM		iKPD_Cols
		LoadX		'F
		AndM
		Push
		GoIfZ		KPD_1
;Have at least one input. Encode 4-bit pattern into a bit number
		GoSub		KPD_Enc4
		Push
		GoIfXEQ		'FF,KPD_Set0	;Not an acceptable pattern
		Store		KPD_Col
KPD_2:	;Wait 20mS then check to see if input is the same
  		Pause		5		;Wait 20mS
		InputFM		iKPD_Cols
		LoadX		'F
		AndM
		GoSub		KPD_Enc4
		Recall		KPD_Col
		Compare
		GoIfNZ		KPD_Set0
KPD_Set3:
		SetMem		KPD_Row,%1000
		SetMem		KPD_Temp,0
KPD_3:
		Recall		KPD_Row		;Bit pattern
		LoadX		'F
		OutputM		oKPD_Rows
		YieldTask			;Allow a bit of time to settle (not critical)
		InputFM		iKPD_Cols
		LoadX		'F
		AndM
		GoSub		KPD_Enc4
		Recall		KPD_Col
		Compare
		GoIfNZ		KPD_3a		;g/no input on this row
		Recall		KPD_Temp
		Recall		KPD_Row
		ORM
		Store		KPD_Temp	;build pattern of row bit that turn on the colum
KPD_3a
		Recall		KPD_Row		;Bit pattern
		Push
		GoIfXEQ		1,KPD_Set4	;Done all rows. Lets see if just one responded
		RORM
		Store		KPD_Row
		GoTo		KPD_3

;Have identified a key. Temp is the row bit pattern. Col is the bit number
KPD_Set4:
		Recall		KPD_Temp	;Should have just one bit set
		GoSub		KPD_Enc4	;Convert to a bit number
		Push
		GoIfXEQ		255,KPD_Set0	;255=more than 1 bit set
		ROLM
		ROLM
		Recall		KPD_Col
		ORM				;Now have 4-bit row-column index
		NVSetPtr	KPD_KeyTable
		GoSub		KPD_TableLook
		Store		KPD_Row
		SetS		sKPD_Flag
KPD_4:
		WaitForSF	sKPD_Flag
		KBeep
		GoTo		KPD_Set0

;Encode 4-bit pattern into a 2-bit number. Return 'FF if  >1 bit
KPD_Enc4:
		NVSetPtr	KPD_Enc4_table
KPD_TableLook:
		LoadX		'F
		AndM				;Defensive!!!
		NVSetPage	0
		NVPopRecNum
		NVSetRecLen	1
		NVPushByte	0
		Return

KPD_GET_Key:
		Recall		KPD_Row
		RecallS		sKPD_Flag
		ClrS		sKPD_Flag
		Return


*******************************************************************************************
**** NVEM0 segment. YOU MUST MANUALLY CUT AND PASTE THIS ON THE *END* OF YOUR PROGRAM *****
**** As you edit make sure your program has only one NVEM0 directive, and that all    *****
**** NVEM page zero stuff is after that directive				      *****
*******************************************************************************************

		NVEM0   ******* Only one NVEM0 per program! *******

;Table to translate from 4-bit pattern to bit number.
;Only patterns with 1 bit set get encoded. Anything else returns FF
KPD_Enc4_table:
;                 0   1   2   3   4   5   6   7   8   9   a   b   c   d   e   f
	NV0Byte	'FF,'00,'01,'FF,'02,'FF,'FF,'FF,'03,'FF,'FF,'FF,'FF,'FF,'FF,'FF

;Table to translate from Row/Col to key code
KPD_KeyTable:
;                RC  RC  RC  RC  RC  RC  RC  RC  RC  RC  RC  RC  RC  RC  RC  RC
;		 00  01  02  03  10  11  12  13  20  21  22  23  30  31  32  33  
	NV0Byte	'01,'02,'03,'80,'04,'05,'06,'81,'07,'08,'09,'82,'83,'00,'84,'85
;TR0601           1   2   3   /   4   5   6   X   7   8   9   -   C   0   .   +

;Test table, produces a hex number where the first digit is Row and the second is Column
******	NV0Byte	'00,'01,02,'03,'10,'11,'12,'13,'20,'21,'22,'23,'30,'31,'32,'33