diff --git a/firmware/README b/firmware/README
index 3095e78c..0e4710e2 100644
--- a/firmware/README
+++ b/firmware/README
@@ -1,3 +1,7 @@
 The firmware is set up for compilation with the GCC toolchain available here:
 
 https://code.launchpad.net/gcc-arm-embedded
+
+Required dependency:
+
+https://github.com/mossmann/libopencm3