Learn how MAX232 works with an illustrated explanation and practical readings.
Follow the labeled connections and functional stages
5 stages · Explore one step at a time
A microcontroller’s UART uses logic levels, while an RS-232 port uses positive and negative voltages. The MAX232 translates between them. It changes voltage levels and polarity; it does not create a baud rate or decode the data.
Connect pin 16 to 5 V and pin 15 to ground. C1 transfers charge in the voltage doubler; C2 supports the inverter. C3 and C4 hold the positive and negative rails, and C5 bypasses the supply. This MAX232 circuit uses 1 µF for all five capacitors.
The diagram’s approximately ±10 V rails explain the unloaded charge-pump action. Actual rails and output swing depend on supply, load and losses.
Microcontroller TX feeds T1IN, pin 11. T1OUT, pin 14, drives the serial line with an inverted bipolar signal: logic HIGH becomes a negative RS-232 voltage, and logic LOW becomes positive. Channel 2 works the same way through pins 10 and 7.
The remote transmitter reaches R1IN, pin 13. The receiver converts the RS-232 signal into a logic output at R1OUT, pin 12, for the microcontroller’s RX input. A negative input gives logic HIGH; a positive input gives LOW. The second receiver uses pins 8 and 9.
The Basic Circuit shows a DCE female DB9 connector from its mating face: pin 2 carries the MAX232’s output, pin 3 accepts the PC’s transmit signal, and pin 5 is signal ground. A straight-through cable joins it to a PC DTE port. TX and RX operate independently, allowing two-way communication.
Choose a channel, change its input and read the output polarity.
Converts the local logic output into an inverted bipolar RS-232 signal.
A HIGH logic input produces a negative RS-232 output. A LOW input produces a positive output.
A second independent transmit path, powered by the same internal charge pump.
A HIGH logic input produces a negative RS-232 output. A LOW input produces a positive output.
Accepts an RS-232 line signal and provides an inverted logic-level output for the local UART.
A positive RS-232 input produces a LOW logic output. A negative input produces a HIGH output.
The second receive path works independently of receiver 1. Both use the common ground reference.
A positive RS-232 input produces a LOW logic output. A negative input produces a HIGH output.
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