The M-mini is a tiny Linux computer with WiFi running OpenWRT.

                  1 3V3
                  x GND
                  x USB+
                  x USB-
                  x RX
                  x TX
                  x RESET_SW
                  x SYS_LED
SPI_CLK  x        x NET_POW
SPI_MISO x        x NET_TX-
SPI_MOSI x        x NET_TX+
IO6/TDI  x        x NET_RX-
IO7/TDO  x        x NET_RX+
TCK      x        x IO18
IO8/TMS  x        x IO19
RESET    x        x IO20

There is a serial console on RX/TX running at 115,200 bits per second.

  _______                     ________        __
 |       |.-----.-----.-----.|  |  |  |.----.|  |_
 |   -   ||  _  |  -__|     ||  |  |  ||   _||   _|
 |_______||   __|_____|__|__||________||__|  |____|
          |__| W I R E L E S S   F R E E D O M
 -----------------------------------------------------
 BARRIER BREAKER (Bleeding Edge, r40555)
 -----------------------------------------------------
  * 1/2 oz Galliano         Pour all ingredients into
  * 4 oz cold Coffee        an irish coffee mug filled
  * 1 1/2 oz Dark Rum       with crushed ice. Stir.
  * 2 tsp. Creme de Cacao
 -----------------------------------------------------

root@Easy-link:/# cat /sys/kernel/debug/gpio 
GPIOs 0-29, ath79:
 gpio-8   (USB power           ) out hi
 gpio-11  (reset               ) in  lo
 gpio-20  (sd-reset            ) in  lo
 gpio-27  (elink:green:system  ) out lo

OpenWRT