I just cannot connect or send AT command from my UNO to A7 AI Thinker module. This is the connection:
UNO -> A7 TX -> RX RX -> TX USB || 5V -> External Power Supply GND -> GND
Without any sketch, I tried to send AT command from serial monitor, and nothing happened.
Different case if I use USB TTL to A7
USB TTL -> A7 VCC (5v) -> 5V GND -> GND TX -> RX RX -> TX
Then it is OK, I can send all AT command, SMS, Call, etc from the serial monitor.
Just what is happening with UNO? Does my UNO RX TX Faulty? How to check it?