COM Express Interfaces
2.20.2. Reference Schematics
2.20.2.1. General Purpose Serial Port Example
Figure 49: General Purpose Serial Port Example
Figure 49: General Purpose Serial Port Example shows the schematic of two general purpose
serial ports with RS232 level shifter (U6). The transistor / inverter combination at the serial TX
and RX lines coming from the Module is necessary to handle the protection against VCC_12V
connection according to chapter 5.10 of COM.0 Rev. 2.1. The MAX3232CD is a dual port RS232
transceiver and handles the level shifting of the TTL signals to the regarding voltage level.
Conformance to the protection scheme defined in COM.0 Rev 2 for pins recovered from the 12V
pool results in a transfer rate limit of about 10 kbaud. If your situation requires higher speeds,
contact your Module vendor for possible work-arounds. The work-arounds likely involve
sacrificing the 12V protection as a tradeoff for higher speeds.
2.20.3. Routing Considerations
No further routing considerations need to be taken.
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COM Express
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