Here’s a X1TXN (AMTX10?) DSM2 module taken from a HP6DSM transmitter. It was easy to install into the Turnigy 9x running the latest er9x firmware. Just three wires, a diode and resistor. It works great!!!

Here’s some photos for your reference.

Front and back of the DSM2 module from the HP6DSM

Here’s the relevant pinout according to this post:
1 GND Module Ground
2 VDD Module power input
3 IRQ Interrupt Request
4 RST Reset, active High
5 MOSI Master out, slave In data
6 nSS Slave Select, Active Low
7 SCLK SPI data clock
8 MISO Master in, slave out data
9 GND Module Ground
10 XOUT Clock output from module
11 TXRX Switch antenna to transmit direction
12 RXTX Switch antenna to receive direction

Here’s a link to the post and schematic on how to hook things up.

Pin out of the X1TXN module. Only pins 1, 2 and 6 are used.

A sample of how you can implement a switch to be able to toggle between the internal DSM module and the module on the back. Here, the white LED glow seen through the speaker grill denote that the internal DSM2 module is ON. The white LED was so bright, I had to put a diffuser in it so that the pilot doesn’t get blinded. I cut the sticker from an MLP4DSM transmitter and used 3M 77 spray adhesive to turn it into a sticker. Gives it that extra fit and finish to complete the mod.

Some reference links: