Chapter 2 – Hardware Information 11IOT Gateway System SRG-33522.3.6 Mini Card Slot (CN21)Pin Signal Description Pin Signal DescriptionTop Side Bottom Side1 2 3.3V3 Reserved**** 4 GND5 Reserved**** 6 1.5V7 CLKREQ# 8 VCC**9 GND 10 I/O**11 REFCLK- 12 CLK**13 REFCLK+ 14 RST**15 N/C or GND 16 VPP**Mechanical key17 Reserved 18 GND19 Reserved 20 Reserved***21 GND 22 PERST#23 PERn0 24 +3.3Vaux25 PERp0 26 GND27 GND 28 +1.5V