; Simple data plotter for SSD1306 72x40 OLED display

(defun init ()
  (with-i2c (s 1 60)
    (writebytes s 0 #x8d #x14 #x20 #x01 #xd9 #xf1 #xad #x30 #xa1 #xaf)))

(defun writebytes (s &rest b)
  (dolist (i b) (write-byte i s)))

(defvar xa 0)
(defvar ya 20)

(defun set (yy byt)
  (if (<= 0 yy 7) (logior byt (ash 1 yy)) byt))

(defun plot (x y)
  (with-i2c (s 1 60)   
    (writebytes s 0 #x21 (+ x 28) (+ x 28) #x22 0 4)
    (restart-i2c s)  
    (write-byte #x40 s)
    (dotimes (p 5)
      (write-byte
       (if (= x xa) #xff 
         (set (- ya (* p 8)) (set (- y (* p 8)) 0))) s))))

(defvar pi 3.14159)

(defun test ()
  (dotimes (x 72)
    (plot x (round (+ 20 (/ (* 22 (sin (/ x pi))) (exp (/ x 36))))))))

(defun clear () (dotimes (x 72) (plot x -1)))