Fail to generate RGB window with L515 on Raspberry Pi 3B+

Dear Sir/Madam,

I have some trouble to generate RGB window on Raspberry Pi 3B+ with L515 camera, belows are some basic information.

Camera: L515

Platfrom: Raspberry Pi 3B+

Port: USB2.1

FW:  01.05.08.01

Error: pipeline.start(config) RuntimeError: Couldn't resolve requests

Description: With in my test file, the depth_frame could be successfully outputed with 320x240, fps: 30, however the color_frame will always lead to a RuntimeError described above.

Test file:

import pyrealsense2 as rs
import numpy as np
import cv2

if __name__ == "__main__":
    # Configure depth and color streams
    pipeline = rs.pipeline()
    config = rs.config()
    config.enable_stream(rs.stream.depth, 320, 240, rs.format.z16, 30)
#     config.enable_stream(rs.stream.color, 320, 240, rs.format.bgr8, 30)
    # Start streaming
    pipeline.start(config)
    try:
        while True:
            # Wait for a coherent pair of frames: depth and color
            frames = pipeline.wait_for_frames()
            depth_frame = frames.get_depth_frame()
#             color_frame = frames.get_color_frame()
            if not depth_frame:
                continue
            # Convert images to numpy arrays

            depth_image = np.asanyarray(depth_frame.get_data())

#             color_image = np.asanyarray(color_frame.get_data())

            cv2.namedWindow('RealSense', cv2.WINDOW_AUTOSIZE)
            cv2.imshow('RealSense', depth_image)
            key = cv2.waitKey(1)
            # Press esc or 'q' to close the image window
            if key & 0xFF == ord('q') or key == 27:
                cv2.destroyAllWindows()
                break
    finally:
        # Stop streaming
        pipeline.stop()