+ *
+ * Voltage values are encoded as a value 0-255 (0-512 on the 5200*),
+ * where the value is a point in the range represented by the vdiv
+ * setting. There are 8 vertical divs, so e.g. 500mV/div represents
+ * 4V peak-to-peak where 0 = -2V and 255 = +2V.