EVM430-I2040S: Serial communications: Isolated RS232 & UART

Hello Avner,

Thank you for your post.

Avner Fernandes said:

Is there any way we can use the isolated RS232 port for 3.3V serial communication?

Yes, this would have to be implemented on the CC3200 side where the RS232-level signals would need to be converted down to 3.3V.

Avner Fernandes said:

I've looked at the schematic, and is the diode-capacitor-transistor arrangement between the DB9 connector & optocouplers some sort of charge pump?

Yes, since the highest supply voltage on the EVM430-I2040S is only 3.3V, these components raise the voltage to the RS232 voltage levels and reduce the voltage down to UART levels. Now, this design uses discrete components to achieve this, but keep in mind that we offer devices that integrate everything into a single package, such as the TRS3122 which is a 2Tx/2Rx Low Voltage, Low Power RS232 Transceiver. To help with your development, you could use the TRS3122EEVM, which converts RS232 signals down to 1.65 V up to 5.5 V, to connect to the CC3200. Another alternative for development could be the following two RS232-to-UART converters:

For your final design, I would not use RS232 but instead use isolators on the UART interface between the MSP430i2040 and the CC3200. For example, the TIDM-TWOPHASEMETER-I2040 has a host processor with isolators between it and the MSP430i2040. I would recommend referring to this design and layout.

Avner Fernandes said:

RS232 voltages can be anywhere between 3 & 25V, and typical systems use around ~12V. What are the voltages we can expect on the DB9 connector?

I measured around +/-12V on the EVM430-I2040S.

Regards,

James

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