Three main steps

1. Conversion from Keras .h5 file to tensorflow .pb file; courtesy of here
   Use following command : python3 keras_to_tensorflow.py -input_model_file <name of the .h5 file>

2. Conversion to tensorflow .tflite file; courtesy of (here)
   Use following command : toco --input_file=<path to generated .pb file>
   --input_format=TENSORFLOW_GRAPHDEF
   --output_format=TFLITE
   --output_file=
   --inference_type=FLOAT
   --input_type=FLOAT
   --input_arrays=<name of your input layer (according to tensorflow naming)> \
   --output_arrays=<name of your output layer (according to tensorflow naming)>
   --input_shapes=1,224,224,3

3. Inference on mobile; courtesy of here