Rs232 connection to gyro, uC and PC
Pin 2 and 3 are connected to uC


According to the information you supplied, those pins are at RS-232 voltage levels. Therefore you must be using a MAX232 or similar to convert those to logic level (TTL or 3.3 V etc) for use by your MCU.

Doesn't it make more sense to use the signals on connector pins 8 &amp; 9 to connect to the MCU instead, since those are already at 3.3 V levels?


  can I use pin 8 and 9 with MAX232 in order to connect the gyro to the PC?


As I explain above, it seems to make more sense (based on the info you supplied) to use the RS-232 signals at pins 2 &amp; 3 for any external RS-232 connection. That way you don't need to add a MAX232 or similar, for the connection to the PC serial port, since the signals would already be at RS-232 levels

Update: Now that you have supplied the Gyro model number, one limitation I noticed in the VectorNav VN-100 Gyro user manual is that a firmware update is only possible via UART #1 which I think is connected to external connector pins 2 &amp; 3 (you need to double-check that). Therefore you need to consider how you would do a firmware update to the Gyro, if you still choose to have pins 2 &amp; 3 connected to the internal MCU.