If you are using the SCL (Serial Clock) and SDA (Serial Data) lines for an I2C bus with the "U1" Heltec WiFi LoRa 32 V2 IoT transceiver, then yes, it is standard practice to use pull-up resistors. These pull-up resistors usually connect each bus line to a positive power supply voltage.

This needs to be done because I2C bus lines idle high and are only driven low by the devices. The pull-up resistor ensures that the line is pulled to a high voltage when no device is driving it low.

Typically, a value between 2.2kΩ and 10kΩ is used for the pull-up resistors, but this may vary depending on your specific requirement, the number of devices on the bus, and the bus speed.

Remember that this is just a general guideline and the specific requirement could be different depending on the Heltec module that you're using. Since I don't have access to your particular model's datasheet or additional details, I would recommend checking the documentation for the specific Heltec Board Module as per my assumption.