Adding max7 example

examples/max7.ms

@@ -0,0 +1,100 @@
+;; A microscheme library for controlling MAX7219 and MAX7221 chips.
+;; These are serially-interfaced 8x8 multiplex drivers, commonly used
+;; for LED arrays and 7-segment displays.
+
+;; ==================== Internal procedures ==================== 
+;;             (These should not be called directly)
+
+(define (shift-out-bits data-pin clock-pin data n)
+	(set-pin data-pin (begin data (asm "ROL CRSh" "ROL CRSh")))
+	(low (high clock-pin))
+	(if (zero? n)
+		#t
+		(begin
+			(shift-out-bits data-pin clock-pin (begin data (asm "LSL CRSl" "ROL CRSh")) (- n 1)))))
+
+(define (noops data-pin clock-pin n)
+	(if (zero? n)
+		#t
+		(begin
+			(shift-out-bits data-pin clock-pin #x0000 15)
+			(noops data-pin clock-pin (- n 1)))))
+
+(define (shift-out chip index data)
+	(let ((data-pin (vector-ref chip 0))
+		  (clock-pin (vector-ref chip 1))
+		  (latch-pin (vector-ref chip 2))
+		  (num (vector-ref chip 3)))
+		(low latch-pin)
+			(noops data-pin clock-pin (- (- num index) 1))
+			(shift-out-bits data-pin clock-pin data 15)
+			(noops data-pin clock-pin index)
+		(high latch-pin)))
+
+;; ==================== External procedures ==================== 
+;;              (These should be called directly)
+
+;; Each chip features one data-in pin and one data-out pin, so that
+;; up to 8 chips can be cascaded together, sharing a single data line.
+;; Each cascade of chips must be initialised using def-max7. The result
+;; is an object used to reference a particular cascade of chips, when it
+;; comes to sending data.
+
+(define (def-max7 data-pin clock-pin latch-pin num)
+	(vector 
+		(low (output data-pin))
+		(low (output clock-pin))
+		(high (output latch-pin))
+		num))
+
+(define (digit chip index dig val)	(shift-out chip index (+ (* dig #x100) val)))
+(define (decode chip index m)		(shift-out chip index (+ #x0900 m)))
+(define (intensity chip index x)	(shift-out chip index (+ #x0A00 x)))
+(define (scan-limit chip index n)	(shift-out chip index (+ #x0B00 n)))
+(define (show chip index state)		(shift-out chip index (if state #x0C01 #x0C00)))
+(define (test chip index state)		(shift-out chip index (if state #x0F01 #x0F00)))
+
+
+;; ======================= Example Usage ======================= 
+
+; (include "working/max7.ms")
+
+; We have 2 max7219 chips cascaded together, on pins 10, 11 and 12
+; (define lcd (def-max7 10 11 12 2))
+; ... connected to a 16-digit 7-segment display!
+
+; We set both chips to decode-mode on all digits:
+; So that we can send numeric characters directly (in BCD)
+; (decode lcd 0 #xFF)
+; (decode lcd 1 #xFF)
+
+; Set the intensity to maximum on both chips:
+; (intensity lcd 0 #x0F)
+; (intensity lcd 1 #x0F)
+
+; Enable all digits on both chips:
+; (scan-limit lcd 0 #x07)
+; (scan-limit lcd 1 #x07)
+
+; Make sure both chips are out of 'shutdown' mode:
+; (show lcd 0 #t)
+; (show lcd 1 #t)
+
+; Now we display the number '0102030405060708'
+
+; (digit lcd 0 1 0)
+; (digit lcd 0 2 1)
+; (digit lcd 0 3 0)
+; (digit lcd 0 4 2)
+; (digit lcd 0 5 0)
+; (digit lcd 0 6 3)
+; (digit lcd 0 7 0)
+; (digit lcd 0 8 4)
+; (digit lcd 1 1 0)
+; (digit lcd 1 2 5)
+; (digit lcd 1 3 0)
+; (digit lcd 1 4 6)
+; (digit lcd 1 5 0)
+; (digit lcd 1 6 7)
+; (digit lcd 1 7 0)
+; (digit lcd 1 8 8)