Which SDK are you using?
Could you please refer the spp_multi_port application.
Please check spp_rx_data_callback(), where the spp RX flow control logic is implemented. (wiced_bt_spp_rx_flow_enable())
Thank you so much for your support.
We are not using SDK.
Now, we use the "CYBT-343026-01 WICED EZ-Serial FE Image V1.1.14".
We'll try to check your proposal.