Index: trunk/psModules/src/camera/pmHDUUtils.c
===================================================================
--- trunk/psModules/src/camera/pmHDUUtils.c	(revision 12768)
+++ trunk/psModules/src/camera/pmHDUUtils.c	(revision 18554)
@@ -9,4 +9,25 @@
 #include "pmFPA.h"
 #include "pmHDUUtils.h"
+
+pmHDU *pmHDUGetFirst (const pmFPA *fpa) {
+
+    // XXX we probably should have an indicator in pmFPA about the depths.
+
+    if (!fpa) return NULL;
+    if (fpa->hdu) return fpa->hdu;
+
+    for (int i = 0; i < fpa->chips->n; i++) {
+	pmChip *chip = fpa->chips->data[i];
+	if (!chip) continue;
+	if (chip->hdu) return chip->hdu;
+	if (!chip->cells) continue;
+	for (int j = 0; j < chip->cells->n; j++) {
+	    pmCell *cell = chip->cells->data[j];
+	    if (!cell) continue;
+	    if (cell->hdu) return cell->hdu;
+	}
+    }
+    return NULL;
+}
 
 pmHDU *pmHDUFromFPA(const pmFPA *fpa)