HTCC-AB01 cannot receive data from other device by serial

Hello everyone。I face a difficult problem。i use cortex-m4 to send data from own serial to the HTCC-AB01’s serial.Moreover,i use line to connect the m4’tx and AB01’s rx.unfortunately,whatever i supply power to each other or use AB01 to supply power to m4.the date i received are all zero

。then i find use m4 to supply power to AB01 can have data,but this situation is temporary , maybe a while time go by ,the data cannot receive。so anybody use this way to send data?this problem botheres me two week,i wish anybody can help me solve this problem!

Connected GND between m4 and AB01? Check what the ABo1 get from serial!

yeh,i connected GND between m4 and AB01,but this problem still existed.

Same baud rate and stop-bit configurations?

yes,these things are all examined i promised。

make a test serial connection without loRAWAN. Put the output to a serial monitor!

Check behavior of deepsleep!