diff --git a/examples/i2c_oled/README.md b/examples/i2c_oled/README.md
index 625a07552f3d2e21353334f551caa36d46d824e9..1d5593e5a4d627f84fb4926d8a446414aa693133 100644
--- a/examples/i2c_oled/README.md
+++ b/examples/i2c_oled/README.md
@@ -9,6 +9,17 @@ various drawing primitives.
 
 https://user-images.githubusercontent.com/1132011/230734071-dee305de-5aad-4ca0-a422-5fb31d2bb0e0.mp4
 
+## Build options
+There are a few build-time options in the i2c.h source:
+* I2C_CLKRATE - currently maxxed out at 100kHz but can be reduced if needed. Higher
+rate support will be added in the future.
+* TIMEOUT_MAX - the amount of tries in busy-wait loops before giving up. This value
+depends on the I2C_CLKRATE and should not affect normal operation.
+* I2C_IRQ - chooses IRQ-based operation instead of busy-wait polling. Useful to
+free up CPU resources but should be used carefully since it has more potential
+mysterious effects and less error checking.
+* IRQ_DIAG - enables timing analysis via GPIO toggling. Don't enable this unless
+you know what you're doing.
 
 ## Use
 Connect an SSD1306-based OLED in I2C interface mode to pins PC1 (SCL) and PC2 (SDA)