User Manual

The signal lines (0, 1, 2, …) are used for sending pulses to servos, controlling digital outputs, and

measuring voltages. The total current limit (in or out) for these pins is 200 mA, but when using the

on-board regulator the current out is limited to 50 mA (see above.)

The RX line is used to receive non-inverted TTL (0–5 V) serial bytes, such as those from

microcontroller UARTs. These bytes can either be serial commands for the Maestro, arbitrary bytes to

send back to the computer via the USB connection, or both. For more information about the Maestro’s

serial interface, see Section 5.a. Note that the Maestro will probably be able to receive 3.3V TTL serial

bytes, but it is not guaranteed to read 3.3V as high on the RX pin, so you should boost 3.3V TTL serial

signals to above 4V if you want to ensure reliable operation.

The TX line transmits non-inverted TTL (0–5 V) serial bytes. These bytes are either generated by the

Mini Maestro itself (as responses to serial commands or arbitrary bytes sent from the computer via the

USB connection), or they come from the TXIN line.

The RST pin can be driven low to reset the Maestro’s microcontroller, but this should not be necessary

for typical applications. The line is internally pulled high, so it is safe to leave this pin unconnected.

Driving RST low is roughly equivalent to powering off the Maestro; it will not reset any of the

configuration parameters stored in non-volatile memory. To reset the configuration parameters, select

Device > Reset to default settings… in the Maestro Control Center.

The ERR line is an output that is tied to the red error/user LED. It is driven high when the red LED is

on, and it is a pulled low through the red LED when the red LED is off. The red LED turns on when

an error occurs, turns off when the error flags have been cleared, and can also be controlled by the

user script. Since the ERR line is never driven low, it is safe to connect the ERR line of multiple Mini

Maestros together. Please note, however, that doing this will cause the red LEDs of all connected Mini

Maestros to turn on whenever one of the Mini Maestros turns on its red LED. For more information on

the possible error conditions and response options, please see Section 4.e.

The TXIN line is a serial input line that makes it easy to chain together multiple Mini Maestros. Any

serial bytes received on this line will be buffered through an AND gate and transmitted on the TX line.

See Section 5.g for more information about daisy chaining.

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