sm-fast.inc structure

MIOS programming (Assembler)
1

I’m trying to teach myself how the scan matrix examples work and was wondering if someone could give me a start here.

In the button handler code there is this…

;; shift 8 times

SM_BUTTON_HANDLER_SHIFT 7

SM_BUTTON_HANDLER_SHIFT 6

SM_BUTTON_HANDLER_SHIFT 5

SM_BUTTON_HANDLER_SHIFT 4

SM_BUTTON_HANDLER_SHIFT 3

SM_BUTTON_HANDLER_SHIFT 2

SM_BUTTON_HANDLER_SHIFT 1

SM_BUTTON_HANDLER_SHIFT 0

Is this section getting values from 8 pins of the DIN for 1 of DOUT or is it getting 1 DIN pin for each of the 8 DOUTs?

Is the loop below looping through the DIN pins or the DOUTs?

;; loop 8 times

incf SM_BUTTON_COLUMN, F, BANKED

movlw 8-1

cpfsgt SM_BUTTON_COLUMN, BANKED

rgoto SM_ButtonHandler_InnerLoop

Which of DIN or DOUT is the column and which is the row?

(What I want to get to eventually is 64 DIN pins with 8 DOUT’s to scan organ keyboards/stops with debouncing.)

Thanks

Graham

2

I think DOUT is the column and DIN is the row. There is a parameter to reverse the polarity of the diodes but I don’t know if that affects the row/column terminology. It might be useful to look at sm_fast.inc as modified by QBas for the 32x32 scan matrix to see how the size of the matrix was altered.

3

Now Graham and I are both trying to really understand sm_fast.inc so that we can create some switch matrix projects. I have commented SM_Init thusly:

;; --------------------------------------------------------------------------
;;  FUNCTION: SM_Init
;;  DESCRIPTION: This function initializes the scan matrix.
;;  It should be called from USER_Init
;;  IN:  -
;;  OUT:  -
;;  USES: BSR
;; --------------------------------------------------------------------------
SM_Init
	;; set button value to initial value (1) for all 64 buttons in data buffer
	lfsr	FSR0, SM_ROW0_VALUE ; FSR0 <- first row address
	movlw	0x08 ; set Reg F as row loop counter
	movwf	TMP1
SM_Init_Loop1
	setf	POSTINC0 ; set all bits for row and increment row address
	decfsz	TMP1, F ; dec loop counter
	rgoto	SM_Init_Loop1

	;; init values of all 64 buttons
	lfsr	FSR0, SM_ROW0_VALUE ; FSR0 <- first row address
	movlw	0x08 ; set Reg F as row loop counter
	movwf	TMP1
SM_Init_Loop2
	setf	POSTINC0 ; set all bits for row and increment row address
	decfsz	TMP1, F ; dec loop counter
	rgoto	SM_Init_Loop2

	;; deselect all columns by setting the DOUT data bit and shifting through all registers
        bcf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK	; clear the shift clock
	bsf	SM_SRIO_LAT_DOUT, SM_SRIO_PIN_DOUT ; set DOUT data bit
	movlw	16 ; 16*8 shifts for up to 16 shift registers
	movwf	TMP1	; Reg F is the register loop counter
SM_Init_Loop3 ; set and clear the DIO Shift Clock 8 times to shift through one pair of registers
        bsf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bcf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bsf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bcf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bsf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bcf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bsf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bcf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bsf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bcf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bsf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bcf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bsf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bcf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bsf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
        bcf    SM_SRIO_LAT_SCLK, SM_SRIO_PIN_SCLK
	decfsz	TMP1, F
	rgoto	SM_Init_Loop3	; loop though 16 pairs of registers

	;; latch DOUT values that were shifted in by clearing and setting the DIO Register Latch Pin
        bcf	SM_SRIO_LAT_RCLK, SM_SRIO_PIN_RCLK
	nop
	nop
	nop
        bsf    SM_SRIO_LAT_RCLK, SM_SRIO_PIN_RCLK

	return

Do have this much right?

Why are the row values set twice, once in SM_Init_Loop1 and then again in SM_Init_Loop2?

4

Why are the row values set twice, once in SM_Init_Loop1 and then again in SM_Init_Loop2?

This seems to be a copy&paste error, in this variant:

http://svnmios.midibox.org/filedetails.php?repname=svn.mios&path=%2Ftrunk%2Fapps%2Fexamples%2Fsm_c_example2%2Fsm_fast.asm

the debounce counters are cleared instead

I think, that the second loop can be savely removed - could you please doublecheck this?

I could give you write access to the repository, so that your additional comments won’t get lost

Best Regards, Thorsten.

5

I think, that the second loop can be savely removed - could you please doublecheck this?

I could give you write access to the repository, so that your additional comments won’t get lost

QBas removed the second loop in his scan matrix enhancements. I removed the second loop with no apparent ill effects. I think it is confirmed that it can be safely removed.

I will contact you regarding repository access when I think my update is ready.

Best Regards,

Jim Henry

6

SM_DOUT_VALUE is a 1 of 8 bit code for the *next* column to be selected by DOUT:

;; determine DOUT value for *next* iteration step
	;; this value gets active with the next latch pulse
	incf	SM_BUTTON_COLUMN, W, BANKED
	call	MIOS_HLP_GetBitANDMask	; (inverted 1 of 8 code)
	movwf	SM_DOUT_VALUE, BANKED

The SM_BUTTON_HANDLER_SHIFT MACRO is used 8 times in each loop of a column select to shift in the 8 bits of the DIN and shift out bits according to SM_DOUT_VALUE to set up DOUT for the next latch which will select the next column. This is the code that chooses when to shift the 0 into the DOUT shift register for the next column select:

;; set DOUT value
	bsf	SM_SRIO_LAT_DOUT, SM_SRIO_PIN_DOUT
	btfss	SM_DOUT_VALUE, 7-bit_number
	bcf	SM_SRIO_LAT_DOUT, SM_SRIO_PIN_DOUT

Because btfss tests bit (7-bit_number) column 0 is selected by Q7 of the DOUT register, column 1 by Q6, and so on. I tried changing the test to simply:

btfss	SM_DOUT_VALUE, bit_number

There were no obvious problems and Q0 selected column 0 etc. which seems easier to deal with for wiring. Any subtlety I’m overlooking?

7

Jim Henry,

I know that your post is old, but what ever happened to your work on the matrix project?

Johnc