rs232 to lvttl
Hello,
the point is that MAX232 (if operated according to the specification) needs 5V supply and thus has 5 V logic output voltage. This shouldn't be connected to 3V operated Bluetooth module. Some modules may tolerate 5 V on serial input, you should check the specification in this regard. If not, you should use a series resistor, e. g. 2.2K or a voltage divider (2.2k series resistor from MAX232 to module RX input, 4.7k from module RX input to ground). For TX line, MAX232 could well operate with 3V signal from module, cause it has 2.0 V (TTL alike) minimal high level.
Regards,
Frank