You can use key codes directly like
adb shell input keyevent 7 # for key ‘0’
adb shell input keyevent 8 # for key ‘1’
adb shell input keyevent 29 # for key ‘A’
adb shell input keyevent 54 # for key ‘B’
we can also send string as a text, like
adb shell input text “ANDROID”
The below text is the whole list of all keyevent names with their
respective codes numbers…
0 –> “KEYCODE_UNKNOWN”
1 –> “KEYCODE_MENU”
2 –> “KEYCODE_SOFT_RIGHT”
3 –> “KEYCODE_HOME”
4 –> “KEYCODE_BACK”
5 –> “KEYCODE_CALL”
6 –> “KEYCODE_ENDCALL”
7 –> “KEYCODE_0”
8 –> “KEYCODE_1”
9 –> “KEYCODE_2”
10 –> “KEYCODE_3”
11 –> “KEYCODE_4”
12 –> “KEYCODE_5”
13 –> “KEYCODE_6”
14 –> “KEYCODE_7”
15 –> “KEYCODE_8”
16 –> “KEYCODE_9”
17 –> “KEYCODE_STAR”
18 –> “KEYCODE_POUND”
19 –> “KEYCODE_DPAD_UP”
20 –> “KEYCODE_DPAD_DOWN”
21 –> “KEYCODE_DPAD_LEFT”
22 –> “KEYCODE_DPAD_RIGHT”
23 –> “KEYCODE_DPAD_CENTER”
24 –> “KEYCODE_VOLUME_UP”
25 –> “KEYCODE_VOLUME_DOWN”
26 –> “KEYCODE_POWER”
27 –> “KEYCODE_CAMERA”
28 –> “KEYCODE_CLEAR”
29 –> “KEYCODE_A”
30 –> “KEYCODE_B”
31 –> “KEYCODE_C”
32 –> “KEYCODE_D”
33 –> “KEYCODE_E”
34 –> “KEYCODE_F”
35 –> “KEYCODE_G”
36 –> “KEYCODE_H”
37 –> “KEYCODE_I”
38 –> “KEYCODE_J”
39 –> “KEYCODE_K”
40 –> “KEYCODE_L”
41 –> “KEYCODE_M”
42 –> “KEYCODE_N”
43 –> “KEYCODE_O”
44 –> “KEYCODE_P”
45 –> “KEYCODE_Q”
46 –> “KEYCODE_R”
47 –> “KEYCODE_S”
48 –> “KEYCODE_T”
49 –> “KEYCODE_U”
50 –> “KEYCODE_V”
51 –> “KEYCODE_W”
52 –> “KEYCODE_X”
53 –> “KEYCODE_Y”
54 –> “KEYCODE_Z”
55 –> “KEYCODE_COMMA”
56 –> “KEYCODE_PERIOD”
57 –> “KEYCODE_ALT_LEFT”
58 –> “KEYCODE_ALT_RIGHT”
59 –> “KEYCODE_SHIFT_LEFT”
60 –> “KEYCODE_SHIFT_RIGHT”
61 –> “KEYCODE_TAB”
62 –> “KEYCODE_SPACE”
63 –> “KEYCODE_SYM”
64 –> “KEYCODE_EXPLORER”
65 –> “KEYCODE_ENVELOPE”
66 –> “KEYCODE_ENTER”
67 –> “KEYCODE_DEL”
68 –> “KEYCODE_GRAVE”
69 –> “KEYCODE_MINUS”
70 –> “KEYCODE_EQUALS”
71 –> “KEYCODE_LEFT_BRACKET”
72 –> “KEYCODE_RIGHT_BRACKET”
73 –> “KEYCODE_BACKSLASH”
74 –> “KEYCODE_SEMICOLON”
75 –> “KEYCODE_APOSTROPHE”
76 –> “KEYCODE_SLASH”
77 –> “KEYCODE_AT”
78 –> “KEYCODE_NUM”
79 –> “KEYCODE_HEADSETHOOK”
80 –> “KEYCODE_FOCUS”
81 –> “KEYCODE_PLUS”
82 –> “KEYCODE_MENU”
83 –> “KEYCODE_NOTIFICATION”
84 –> “KEYCODE_SEARCH”
85 –> “TAG_LAST_KEYCODE”
From https://groups.google.com/forum/#!topic/android-developers/pHBcP2JBT5A