updating rtc code

lisp/rtc.lsp

@@ -15,6 +15,12 @@ Number must be in the range 0 to 99."
     (ash (floor x 10) 4)
     (logand (rem x 10) #xf)))
 
+(defun rtc-p ()
+  "(rtc-p)
+Returns t if the RTC is connected."
+  (with-i2c (str *rtc-port* #x68)
+	    (streamp str)))
+
 (defun rtc-set (h m s)
  "(rtc-set hr min sec)
 Set the time on a DS3231 RTC. Times are in BCD, so use
@@ -27,7 +33,7 @@ for 12:34:00."
 	      (write-byte 0 str)
 	      (write-byte s str)
 	      (write-byte m str)
-	      (write-byte h str)))
+	      (write-byte h str))))
 
 (defun rtc-get ()
   (with-i2c (str *rtc-port* #x68)
@@ -49,4 +55,3 @@ Set the time using the RTC."
   "(now-rtc)
 Sets the RTC time using the now function."
   (apply rtc-set (now)))
-