diff --git a/README.md b/README.md
index a62c450..2f8cee2 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,8 @@
 # ST7567 I2C display driver
 For esp-idf, same idea as the st7920 driver
 
+This is the I2C version, also see [SPI version](https://git.drath.cc/drath/esp-st75670-spi)
+
 ## Usage
 
 ```c
@@ -19,7 +21,7 @@ st7567_config_t cfg = {
     .i2c_bus = bus,
     .i2c_addr = ST7567_I2C_ADDR_DEFAULT, // 0x3F,
     .i2c_clock_speed_hz = 400000,
-    .contrast = 0x39,  // good for generic modules at 3.3v
+    .contrast = 0x38,  // good for generic modules at 3.3v
 };
 st7567_device_t dev;
 st7567_init(&cfg, &dev);