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Interfase MAX3221

Jorge Lopez Ambrosioni
Prodigy 30 points
Other Parts Discussed in Thread: MAX3221

I am using two max3221 to communicate a Raspberry Pi3 (serial port 3.3V TTL output) with an arduino (serial port 5V TTL output) via Rs232. Each interphase separates works well when connecting to a PC.
 RBP <-> MAX3221 <-> PC
 Arduino <-> MAX3221 <-> PC
But when wanting to communicate the arduino with the Raspberry I can neither send or receive data
 RBP <-> MAX3221 <-> MAX3221 <-> Arduino
Both MAX3221 are configured with Automatic power-down Enabled. Does anyone have any idea?

Arduino implementation

Raspberry implementation

  • 0
    TI__Guru 62920 points
    Hi Jorge,

    If automatic power-down is enabled on both sides, the link may not be able to start up. This feature automatically disables the driver if no valid RS-232 input signal is detected at the receiver port. This means that one side needs to be enabled and driving a valid high or low level to signal to the other side that it needs to power up.

    Another thing you may want to check is the pin assignments on your connector/cable. You want to make sure that TX lines are routed to RX lines and vice-versa. If certain lines need to be swapped when connecting between the RBP and Arduino you may be able to use a null modem (cross-linked) cable or adapter to resolve the issue.

    Regards,
    Max
  • 0 in reply to Miguel Robertson
    Prodigy 30 points
    Thank Max, that was it. Disabling the automatic power-down on one of the sides worked.