diff --git a/CCU/README.md b/CCU/README.md
index 45c64b61a..3ff70c299 100644
--- a/CCU/README.md
+++ b/CCU/README.md
@@ -8,4 +8,4 @@ FIXME For testing on a Nucleo, use HSI; otherwise use HSE whenever possible
 
 GR26 CCU is the GR25 ECU (aka GR25 Big Bird)
 
-Requires using the serial port to send `C` to toggle charging and any other input to disable it
+Requires using the serial port to send `C` to toggle charging and any other input to disable it. Send '?' for state data