usbdux: usbduxsigma: fixed timing issues between ADC and DAC

When sync ADC and the DAC was running at the same time the ADC
showed spikes in the signal. This happened when just before the
DRDY from the ADC was triggered a DAC interrupt was dealt with.
ADC and DAC share the same SPI bus and priority is now given the
ADC. The DAC values are now first stored in a buffer and
are only send to the DAC once the ADC has finished
converting all channels (start = 0) so that the SPI bus is
definitely quiet for about 100us.

Signed-off-by: Bernd Porr <mail@berndporr.me.uk>
Signed-off-by: Kyle McMartin <kyle@kernel.org>

usbdux/usbduxsigma_firmware.asm

@@ -30,17 +30,20 @@
 	
 	.inc	fx2-include.asm
 
-;;; a couple of flags
+;;; a couple of flags in high memory
 	.equ	CMD_FLAG,80h	; flag for the next in transfer
 	.equ	PWMFLAG,81h	; PWM on or off?
 	.equ	MAXSMPL,82H	; maximum number of samples, n channellist
 	.equ	MUXSG0,83H	; content of the MUXSG0 register
-	.equ	SMPLCTR,84h
-	.equ	DPTRL,85H
-	.equ	DPTRH,86h
-	.equ	ASYNC_ON,87h
 	.equ	INTERVAL,88h	; uframe/frame interval
 	.equ	INTCTR,89h	; interval counter
+	.equ	DABUFFER,0F0h	; buffer with DA values
+
+;;; in precious low memory but accessible within one clock cycle
+	.equ	DPTRL,70H
+	.equ	DPTRH,71h
+	.equ	ASYNC_ON,72h
+	.equ	SMPLCTR,73h
 
 ;;; actual code
 	.org	0000h		; after reset the processor starts here
@@ -229,31 +232,24 @@ isr0:
 	push	06h		; R6
 	push	07h		; R7
 
-	mov	r0,#ASYNC_ON
-	mov	a,@r0
+	mov	a,ASYNC_ON
 	jz	noepsubmit
 
 	mov	DPS,#0
-	mov	r0,#DPTRL
-	mov	dpl,@r0
-	inc	r0
-	mov	dph,@r0
+	mov	dpl,DPTRL
+	mov	dph,DPTRH
 
 	lcall	readADCch	; read one channel
 
-	mov	r0,#DPTRL
-	mov	@r0,dpl
-	inc	r0
-	mov	@r0,dph
+	mov	DPTRL,dpl
+	mov	DPTRH,dph
 
-	mov	r0,#SMPLCTR
-	mov	a,@r0
+	mov	a,SMPLCTR
 	dec	a
-	mov	@r0,a
+	mov	SMPLCTR,a
 	jnz	noepsubmit
 
-	mov	r0,#ASYNC_ON
-	mov	@r0,#0
+	mov	ASYNC_ON,#0
 
 	clr	IOA.7		; START = 0
 	
@@ -303,9 +299,6 @@ main:
         mov     a,#00000011b    ; allows skip
         lcall   syncdelaywr
 
-	mov	IP,#0		; all std 8051 int have low priority
-	mov	EIP,#0FFH	; all FX2 interrupts have high priority
-	
 	mov	dptr,#INTSETUP	; IRQ setup register
 	mov	a,#08h		; enable autovector
 	lcall	syncdelaywr
@@ -314,6 +307,9 @@ main:
 	mov	a,#0
 	lcall	syncdelaywr
 
+	mov	IP,#01H		; int0 has highest interrupt priority
+	mov	EIP,#0		; all USB interrupts have low priority
+
 	lcall	initAD		; init the ports to the converters
 
 	lcall	initeps		; init the isochronous data-transfer
@@ -341,8 +337,10 @@ initAD:
 	mov	r0,#MAXSMPL	; length of channellist
 	mov	@r0,#0		; we don't want to accumlate samples
 
-	mov	r0,#ASYNC_ON	; async enable
-	mov	@r0,#0		; we don't want to accumlate samples
+	mov	ASYNC_ON,#0	; async enable
+
+	mov	r0,#DABUFFER
+	mov	@r0,#0
 
 	mov	OEA,#11100000b	; PortA7,A6,A5 Outputs
 	mov	IOA,#01100000b	; /CS = 1 and START = 0
@@ -589,8 +587,6 @@ sof_isr:
 	push	06h		; R6
 	push	07h		; R7
 
-	clr	IE.7		; make sure that no other int's disturbe us
-
 	mov	r0,#INTCTR	; interval counter
 	mov	a,@r0		; get the value
 	dec	a		; decrement
@@ -631,18 +627,14 @@ sof_adc:
 	mov	a,#0		; just zero
 	movx	@dptr,a		; pad it up
 	inc	dptr		; algin along a 32 bit word
-	mov	r0,#DPTRL
-	mov	@r0,dpl
-	inc	r0
-	mov	@r0,dph
+	mov	DPTRL,dpl
+	mov	DPTRH,dph
 
 	mov	r0,#MAXSMPL
 	mov	a,@r0
-	mov	r0,#SMPLCTR
-	mov	@r0,a
+	mov	SMPLCTR,a
 
-	mov	r0,#ASYNC_ON
-	mov	@r0,#1		; enable data collection
+	mov	ASYNC_ON,#1
 
 epfull:
 	;; do the D/A conversion
@@ -659,6 +651,12 @@ epfull:
 	lcall	syncdelaywr	; wait for the rec to sync
 
 epempty:
+	mov	a,IOA		; conversion running?
+	jb	ACC.7,sofend
+
+	lcall	DAsend
+
+sofend:	
 	;; clear INT2
 	mov	a,EXIF		; FIRST clear the USB (INT2) interrupt request
 	clr	acc.4
@@ -669,8 +667,6 @@ epempty:
 	movx	@DPTR,a
 
 nosof:
-	setb	IE.7		; re-enable global interrupts
-	
 	pop	07h
 	pop	06h
 	pop	05h
@@ -795,8 +791,6 @@ ep1out_isr:
 	push	06h		; R6
 	push	07h		; R7
 
-	clr	IE.7		; block other interrupts
-		
 	mov	dptr,#0E780h	; FIFO buffer of EP1OUT
 	movx	a,@dptr		; get the first byte
 	mov	r0,#CMD_FLAG	; pointer to the command byte
@@ -831,8 +825,7 @@ pwm_off:
 	sjmp	over_da
 
 initsgADchannel:
-	mov	r0,#ASYNC_ON
-	mov	@r0,#0		; make sure that no async activity is on
+	mov	ASYNC_ON,#0
 	
 	mov	dptr,#0e781h	; FIFO buffer of EP1OUT
 	lcall	configADC	; configures the ADC esp sel the channel
@@ -869,13 +862,11 @@ startadc2:
 	inc	dptr
 	mov	r0,#MAXSMPL
 	mov	@r0,a 		; length of the channel list
-	mov	r0,#SMPLCTR
-	mov	@r0,a
+	mov	SMPLCTR,a
 
 	lcall	configADC	; configures all registers
 
-	mov	r0,#ASYNC_ON	; async enable
-	mov	@r0,#1		; enable it
+	mov	ASYNC_ON,#1	; async enable
 
 	lcall	reset_ep6	; reset FIFO
 	
@@ -958,8 +949,6 @@ over_da:
 	mov	a,#00001000b	; clear the ep1outirq
 	movx	@DPTR,a
 
-	setb	IE.7		; re-enable interrupts
-
 	pop	07h
 	pop	06h
 	pop	05h
@@ -979,19 +968,45 @@ over_da:
 
 
 	
-;;; all channels
+;;; save all DA channels from the endpoint buffer in a local buffer
 dalo:
 	movx	a,@dptr		; number of bytes to send out
 	inc	dptr		; pointer to the first byte
+	mov	r1,#DABUFFER	; buffer for DA values
+	mov	@r1,a		; save it
+	inc	r1		; inc pointer to local buffer
 	mov	r0,a		; counter
-nextDA:	
+nextDAlo:	
 	movx	a,@dptr		; get the byte
 	inc	dptr		; point to the high byte
-	mov	r3,a		; store in r3 for writeDA
+	mov	@r1,a		; save it in the buffer
+	inc	r1
 	movx	a,@dptr		; get the channel number
 	inc	dptr		; get ready for the next channel
+	mov	@r1,a		; save it
+	inc	r1
+	djnz	r0,nextDAlo	; next channel
+	ret
+
+
+;;; write to the DA converter
+DAsend:
+	mov	r1,#DABUFFER	; buffer of the DA values
+	mov	a,@r1		; get the channel count
+	jz	DAret		; nothing to do
+	inc	r1		; pointer to the first byte
+	mov	r0,a		; counter
+nextDA:	
+	mov	a,@r1		; get the byte
+	inc	r1		; point to the high byte
+	mov	r3,a		; store in r3 for writeDA
+	mov	a,@r1		; get the channel number
+	inc	r1		; get ready for the next channel
+	push	1		; is modified in the subroutine
 	lcall	writeDA		; write value to the DAC
+	pop	1		; get the pointer back
 	djnz	r0,nextDA	; next channel
+DAret:	
 	ret
 
 
@@ -1014,7 +1029,7 @@ writeDA3:
 	rr	a		; shift to the upper to the lower
 	djnz	r1,writeDA3
 	orl	a,r2		; merge with the channel info
-	clr	IOA.6		; /SYNC of the DA to 0
+	clr	IOA.6		; /SYNC (/CS) of the DA to 0
 	lcall	sendSPI		; send it out to the SPI
 	mov	a,r3		; get data again
 	anl	a,#00001111b	; get the lower nibble
@@ -1024,7 +1039,7 @@ writeDA4:
 	djnz	r1,writeDA4
 	anl	a,#11110000b	; make sure that's empty
 	lcall	sendSPI
-	setb	IOA.6		; /SYNC of the DA to 1
+	setb	IOA.6		; /SYNC (/CS) of the DA to 1
 noDA:	ret