X100 full pinout (signals other than TX/RX/GND/VBat may be slightly different in other models):
There are two numbering schemes - with pins counted from left to right and with pins counted from right to left (phone is keypad up).
Pin left-to-right Pinright-to-left Signal Description
1,2 18,17 V_EXT_CHARGE charge input
3 16 AUX_SPK handsfree speaker out
4 15 TXD1 serial 2 out for debugging
5 14 +Vbat accumulator out
6,8,11 8,11,13 GND
7 12 REC01 power on/off sch input
9 10 RXD1 serial 2 in for debugging
10 9 AUX_MIC handsfree mic in
12 7 CHARGER_OK power on/off and charging control
13 6 JIG_REC power on/off scheme control
14 5 CTS serial 1 CTS
15 4 RTS serial 1 RTS
16 3 RxD serial 1in used for data/ flash cable
17 2 TxD serial 1 out used for data/ flash cable
18 1 +Vbat accumulator out