enable RTC

diff --git a/README.md b/README.md
index 293910d..32f5e23 100644 (file)
--- a/README.md
+++ b/README.md
@@ -4,8 +4,26 @@ This is my attempt at using open source tools to generate bitstream
 
 Run `make prog` to load the example to the board.
 
+
+## enable RTC
+
+Add to config.txt:
+
+```
+dtoverlay=i2c-rtc,ds1307
+```
+
+or execute in shell:
+
+```
+echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-1/new_device
+```
+
+
 ## read HAT ID eeprom
 
 Add to config.txt:
 
+```
 dtoverlay=i2c-gpio,i2c_gpio_sda=0,i2c_gpio_scl=1,bus=4
+```