User Manual

The Mini Maestro 12, 18, and 24 have a special input called TXIN that eliminates the need for an

external AND gate (the AND gate is built in to the Maestro.) To make a chain of devices using the

TXIN input, connect them like this:

Daisy chaining serial devices that have a TXIN input.

Using a PC and a Maestro together as the master device

The Maestro can enable a personal computer to be the master device. The Maestro must be

connected to a PC with a USB cable and configured to be in either USB Dual Port or USB Chained

serial mode. In USB Dual Port mode, the Command Port on the PC is used for sending commands

directly to the Maestro, and the TTL Port on the PC is used to send commands to all of the slave

devices. In the USB Chained mode, only the Command Port is used on the PC to communicate with

the Maestro and all of the slave devices. Select the mode that is most convenient for your application

or easiest to implement in your programming language.

Using a Maestro as a slave device

The Maestro can act as a slave device when configured to be in the UART serial mode. In this mode,

commands are received on the RX line, and responses are sent on the TX line. A USB connection to

a PC is not required, though an RX-only Comand Port is available on the PC for debugging or other

purposes.

Connections

Connect the TX line of the master device to the RX lines of all of the slave devices. Commands sent

by the master will then be received by all slaves.

Receiving serial responses from one of the slave devices on the PC can be achieved by connecting

the TX line of that slave device to the RX line of the Maestro.

Receiving serial responses from multiple slave devices is more complicated. Each device should only

transmit when requested, so if each device is addressed separately, multiple devices will not transmit

simultaneously. However, the TX outputs are driven high when not sending data, so they cannot simply

be wired together. Instead, you can use an AND gate, as shown in the diagram, to combine the

signals. Note that in many cases receiving responses is not necessary, and the TX lines can be left

unconnected.

5. Serial Interface Page 60 of 99