====== CPI-C IO Features ======

===== Rear Panel IO =====

The CPi-C series panel PCs have a 26-pin header socket on the rear panel with the following pinout.

{{ :comfilepi:io26.png?nolink |}}
See pp.8 of the [[https://datasheets.raspberrypi.com/cm4/cm4-datasheet.pdf|Compute Module 4 datasheet]] for more information.

The GPIO pins are not exposed through a level shifter like the CPi-S panel PCs, so the internal pull-up/-down resistors can be utilized.  GPIO45 has an internal 1.8kohm pullup resistor to 3.3V because it is initially used for I2C (See Table 6 of the [[https://datasheets.raspberrypi.com/cm4/cm4-datasheet.pdf|Compute Module 4 datasheet]]).

The 5V pins can supply a maximum current of 1A.  The 3.3V pins can supply a maximum current of 700mA.  If both 5V and 3.3V rail pins are used simultaneously, their total power should be kept below 5 watts.

The panel PC's RTC is connected to I2C1, so those pins assigned to I2C1 should not be reconfigured.

===== Underside IO =====

The underside of the CPi-C panel PCs expose 12~24VDC power input, 1 RS-232 serial port, 1 RS-485 serial port, 3 USB 2.0 ports, an I2C port, 5V power output, and an RJ45 Ethernet port.

{{ :comfilepi:comfilepibackcon.png |}}

Please note that the I2C pins (SDA and SCL) are 3.3V; the 5V pin is supplied to ensure users have enough voltage and current to power their external devices and does not imply a 5V I2C port.

The USB device port dedicated to [[https://www.comfilewiki.co.kr/en/doku.php?id=comfilepi:raspbian:index#installation_instructions|programming the Compute Module's eMMC]].


==== Side Panel IO ====

The right panel of the CPi-C panel PCs exposes a MicroSD card slot and a stereo audio output jack.    

{{ :comfilepi:pinout4.png?300 |}}

For models with an eMMC, the MicroSD card slot is not electrically connected, so it cannot be used.