diff --git a/Code/thermal_printer/README.md b/Code/thermal_printer/README.md
index 6a8ec9f..6b1bb7e 100644
--- a/Code/thermal_printer/README.md
+++ b/Code/thermal_printer/README.md
@@ -16,11 +16,28 @@
 
 #### ESC ! n  
 set printer font index,n:0-4  
-`echo -en "\x1b\x21\x0" > /tmp/DEVTERM_PRINTER_IN`  
-`echo -en "\x1b\x21\x1" > /tmp/DEVTERM_PRINTER_IN`  
-`echo -en "\x1b\x21\x2" > /tmp/DEVTERM_PRINTER_IN`  
-`echo -en "\x1b\x21\x3" > /tmp/DEVTERM_PRINTER_IN`  
-`echo -en "\x1b\x21\x4" > /tmp/DEVTERM_PRINTER_IN`  
+`echo -en "\x1d\x21\x0" > /tmp/DEVTERM_PRINTER_IN`  
+`echo -en "\x1d\x21\x1" > /tmp/DEVTERM_PRINTER_IN`  
+`echo -en "\x1d\x21\x2" > /tmp/DEVTERM_PRINTER_IN`  
+`echo -en "\x1d\x21\x3" > /tmp/DEVTERM_PRINTER_IN`  
+`echo -en "\x1d\x21\x4" > /tmp/DEVTERM_PRINTER_IN`  
+
+##### ascii font size 
+1. 0 = 8x16
+1. 1 = 5x7
+1. 2 = 6x12
+1. 3 = 7x14
+1. 4 = 8x16
+
+##### unicode font size  
+
+1. 0 = 12x12
+1. 1 = 14x14
+1. 2 = 16x16
+1. 3 = 18x18
+1. 4 = 20x20
+
+
 
 https://github.com/clockworkpi/DevTerm/blob/81addc7f4ba1eb4acb2f59fb1fef70386dbe1f0d/Code/thermal_printer/devterm_thermal_printer.c#L381
 
@@ -42,15 +59,16 @@ then restart devterm-printer.service with
 ```
 sudo systemctl restart devterm-printer
 ```
-devterm-printer daemon will auto detect if the ttf file existed,if exists, devterm-printer will use the ttf as default font  
-if ttf file not existed, devterm-printer will fallback to ascii mode  
-
-use above  set printer font index,n:0-4 command to set font size, 
-1. 0 = 12x12
-1. 1 = 14x14
-1. 2 = 16x16
-1. 3 = 18x18
-1. 4 = 20x20
+devterm-printer daemon will auto detect the ttf font file
+ 
+#### switch to UNICODE MODE  
+```
+echo -en "\x1b\x21\x1" > /tmp/DEVTERM_PRINTER_IN  
+```
+#### switch back to default ASCII mode  
+```
+echo -en "\x1b\x21\x0" > /tmp/DEVTERM_PRINTER_IN  
+```
 
 then