Firmware update for Tic Stepper Motor Controllers, with new features including limit switches and homing

Connecting a limit switch to the Tic (SCL, SDA, TX, and RX pins).

To go along with last week’s release of the Tic T249, we have also released a new version of the Tic firmware (version 1.06) for all Tic stepper motor controllers that adds several new features.

By popular demand, this new firmware version adds support for limit switches: any of the Tic control pins (SCL, SDA, TX, RX, or RC) can be configured as a digital input for a forward or reverse limit switch. When the limit switch is active, the Tic abruptly shuts down any movement in the specified direction, but allows the stepper motor to move in the other direction. You can use limit switches to help prevent your system from leaving its desired range of motion.

If you configure a limit switch, you can use the Tic’s new homing procedure. The new “Go home” command, which is available over serial, I²C, and USB, starts the homing procedure. The Tic will move in the direction specified by the command until it hits a limit switch for that direction. Then it will change directions, move until the limit switch deactivates, and set its current position to 0. The stepping speeds used by the Tic during the homing procedure are configurable.

You can also use the homing feature automatically, without sending a command. If automatic homing is enabled, the Tic performs the homing procedure whenever it is being commanded to go to a specific position but it is uncertain of its current position (e.g. immediately after motor power is applied). This feature can be handy if you are controlling the position of your stepper motor using an RC, analog, or quadrature encoder signal.

We have added a new section to the Tic user’s guide with detailed instructions for setting up limit switches and homing.

Example pin configuration for a Tic with limit switches.

New homing settings added in Tic firmware version 1.06.

The new firmware version also adds several features to the Tic’s TTL serial interface that make it more usable in systems with large numbers of Tics and in half-duplex serial busses. Specifically, it adds support for an alternative device number so any Tic can optionally be addressed by two different device numbers, and it adds an option to enable 14-bit device numbers so you can have more than 128 devices on a serial bus. The new firmware version also has an option to encode its serial responses using only bytes between 0 and 127, which can be useful in setups where the serial response from one Tic will be seen by other Tic devices, and you don’t want it to be misinterpreted as a command. We also implemented several changes to make the Tic less susceptible to noise on the serial lines, and you can now enable CRC bytes for serial responses sent by the Tic so that you can confirm the data you received matches what the Tic sent.

The Tic T249 was released with the latest firmware, so it has all of these new features, and we will be upgrading our existing Tics to this firmware version as we manufacture more. To gain access to these new features on your existing Tic controllers, you can download the latest configuration software and upgrade your device’s firmware to version 1.06. For more information, see the firmware upgrade instructions in the Tic user’s guide.

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