diff --git a/readme.md b/readme.md
index 6c34259..a181459 100644
--- a/readme.md
+++ b/readme.md
@@ -3,6 +3,7 @@
 - [Atmega 32U4 datasheet](https://ww1.microchip.com/downloads/en/devicedoc/atmel-7766-8-bit-avr-atmega16u4-32u4_datasheet.pdf)
 - [Atmel SAM3X/3A datasheet](https://copperhilltech.com/content/Atmel-SAM3X-Datasheet.pdf)
 - [Atmega 32U4 AVR035: Efficient C Coding for AVR](https://ww1.microchip.com/downloads/en/Appnotes/doc1497.pdf)
+- [Arduino Due timer/counter overview](https://github.com/ivanseidel/DueTimer/blob/master/TimerCounter.md)
 
 ### ELM327
 - [AT commands](https://www.sparkfun.com/datasheets/Widgets/ELM327_AT_Commands.pdf)
@@ -35,4 +36,4 @@ STATES:
 - display each letter of initializing...
 - display counter values and device info
 - display bluetooth state
-- update everything
\ No newline at end of file
+- update everything