Prevent going out of bounds with DAC offset.

DSTAT-temp/src/max5443.c

@@ -7,7 +7,7 @@
 
 #include <max5443.h>
 
-volatile uint16_t max5443_offset = 105;
+volatile int16_t max5443_offset = 105;
 
 struct usart_spi_device spi_device_conf_c = {
           .id = IOPORT_CREATE_PIN(PORTC, 4)
@@ -31,8 +31,13 @@ void max5443_set_voltage1(uint16_t dacindex){
 		
 // 	if (buffer.ui16 == dacindex)
 // 		return;
-		
-	buffer.ui16 = dacindex+max5443_offset;
+	
+	if (65535-dacindex < max5443_offset)
+		buffer.ui16 = 65535;
+	else if (dacindex < -1*max5443_offset)
+		buffer.ui16 = 0;
+	else
+		buffer.ui16 = dacindex+max5443_offset;
 	
  	irqflags_t flags;
      flags = cpu_irq_save();