diff --git a/src/ctapipe_io_lst/pixels.py b/src/ctapipe_io_lst/pixels.py
index f2e23101..41d2d00a 100644
--- a/src/ctapipe_io_lst/pixels.py
+++ b/src/ctapipe_io_lst/pixels.py
@@ -25,8 +25,11 @@ def get_pixel_table_from_camera_config(config):
     n_pixels = len(pixel_id_map)
 
     pixel_index = np.arange(n_pixels)
+    # the pixel data arrives in module groups, the module id of each group
+    # is in module_id_map. Repeat to have the module_id of each pixel
     module_id = np.repeat(module_id_map, N_PIXELS_MODULE)
 
+    # pixels inside one module are ordered by module_pixel_index
     module_pixel_index = np.tile(np.arange(N_PIXELS_MODULE), n_modules)
     hardware_pixel_id = module_id * N_PIXELS_MODULE + module_pixel_index