So, we can find that:

– 1. If uart1 applies hardware flow control, uart2 could NOT
– 2. If uart2 applies hardware flow control, uart1 could NOT
– 3. If uart3 applies hardware flow control, uart2 can NOT be used
– 4. At most, only two uart port can anpply haredware flow control
simultaneously, they are uart1 and uart3, but uart2 can NOT be used
– 5. If only one port allplies hardware flow control, others are non flow
control or software flow control, either uart1 or uart 2 applies(hw. flow

control).

Uart Rx/Tx pin are high level in idle state, so please pay attention to it
– Being complex with earphone R/L-chaneel can cause current leaking

[A]: 1. when BB is sleeping, uart works nothing

ICfans
2. when BB is sleeping, uart misses all data form external module
3. there is no method to know BB when to sleep, or you can not judge
whether it is sleep(because while sleeping, no scripts are running)
But you can judge from 26M clock(all other clock generated based on it),
uart RTS pin to get information of BB sleep
4. you can using AT+ESLP=0/1 to disable/enable BB sleep or call kal_bool
l4c_em_sleep_mode_req(kal_bool on_off);

Or using the following API:
– extern kal_bool l4c_em_sleep_mode_req(kal_bool on_off);