-extern __pdata int16_t ao_sample_pres; /* most recent pressure sensor reading */
-extern __pdata int16_t ao_sample_alt; /* MSL of ao_sample_pres */
-extern __pdata int16_t ao_sample_height; /* AGL of ao_sample_pres */
+extern __pdata pres_t ao_sample_pres; /* most recent pressure sensor reading */
+extern __pdata alt_t ao_sample_alt; /* MSL of ao_sample_pres */
+extern __pdata alt_t ao_sample_height; /* AGL of ao_sample_pres */