* Set this to the number of combos that you're using in the [Combo](feature_combo.md) feature.
* `#define COMBO_TERM 200`
* how long for the Combo keys to be detected. Defaults to `TAPPING_TERM` if not defined.
+* `#define TAP_CODE_DELAY 100`
+ * Sets the delay between `register_code` and `unregister_code`, if you're having issues with it registering properly (common on VUSB boards). The value is in milliseconds.
## RGB Light Configuration
* `#define USE_I2C`
* For using I2C instead of Serial (defaults to serial)
+* `#define SOFT_SERIAL_PIN D0`
+ * When using serial, define this. `D0` or `D1`,`D2`,`D3`,`E6`.
+
# The `rules.mk` File
This is a [make](https://www.gnu.org/software/make/manual/make.html) file that is included by the top-level `Makefile`. It is used to set some information about the MCU that we will be compiling for as well as enabling and disabling certain features.