diff --git a/cfg/avr.cfg b/cfg/avr.cfg
index ee5aa92bb..e93db947d 100644
--- a/cfg/avr.cfg
+++ b/cfg/avr.cfg
@@ -117,5 +117,16 @@
   <define name="tanhf" value="tanh"/>
   <define name="truncf" value="trunc"/>
   <!-- The rest of the trigonometric functions are defined in std.cfg -->
-  <!-- setjmp.h -->         
+  <!-- stdio.h -->
+  <define name="fdev_set_udata(stream, u)" value="do { (stream)- > udata = u; } while(0)"/>
+  <define name="fdev_get_udata(stream)" value="((stream)- > udata)"/>
+  <define name="_FDEV_SETUP_READ" value="__SRD"/>
+  <define name="_FDEV_SETUP_WRITE" value="__SWR"/>
+  <define name="_FDEV_SETUP_RW" value="(__SRD | __SWR)"/>
+  <define name="_FDEV_ERR" value="(-1)"/>
+  <define name="_FDEV_EOF" value="(-2)"/>
+  <define name="putc(__c, __stream)" value="fputc(__c, __stream)"/>
+  <define name="putchar(__c)" value="fputc(__c, stdout)"/>
+  <define name="getc(__stream)" value="fgetc(__stream)"/>
+  <define name="getchar()" value="fgetc(stdin)"/>  
 </def>