4.5.10. Serial port¶
Controller allows control through UART serial port with TTL 3.3 V logic. UART outputs are located on BPC connector. Because of widespread availability of UART and adapters to USB, Bluetooth, Ethernet and other standard interfaces there is an option for wireless control (Bluetooth) or control over the internet (Ethernet). UART data protocol is the same as USB data protocol. I.e. it is enough to enable nonstandard serial port polling in XiLab or in libximc and the device will be found if response delay doesn’t exceed two seconds. It is also possible to control controller with the help of other independently programmed micro-controller, however in this case it will be required to support controller communication protocol.
UART supports the following settings.
| Transfer rate | 9600-921600 bit/sec |
| Data bits | 8 |
| Parity | enabled or disabled |
| Parity type | even, odd, space, mark |
| Stop bits | 1 or 2 |
4.5.10.1. Standard connection settings¶
The COM-port parameters are fixed controller-side. Use the following standard settings to connect to the controller via UART:
| Speed | 115200 baud |
| Data bits | 8 |
| Parity | none |
| Stop bits | 2 |
| Flow control | none |
| Byte receive timeout | 400 ms |
Note
To connect to the controller via UART one should first connect to it via USB or Ethernet and set the required speed, parity and stop bits, then save the settings to the non-volatile memory. If you cannot connect, use the standard settings listed above. A complete description of the protocol is given in Communication protocol specification.
| Logic type | TTL 3.3 V |
| Maximum data transfer speed | 921 kbit |
| Nominal output current | 5 mA |
4.5.10.2. Serial port connection diagram¶
Warning
High data transfer speeds through long cables (the cable must be up to 5 meters long) in case of electromagnetic interference are impossible. If transfer errors do occur, use RC filtering circuits and reduce transfer speeds so that characteristic time of an RC-circuit is at least 4 times less than time needed to transfer a single bit. RC-circuit characteristic time is chosen based on the circumstances.
4.5.10.2.1. Controller board serial port connection¶
For the controller board UART outputs are located on the BPC connector.
Recommended scheme of connection to serial port pins for the controller board
4.5.10.2.2. One-axis and two-axis systems serial port connection¶
Two-axis and one-axis systems has UART outputs. Corresponding contacts for each axis output on the HDB-26 connector.
Recommended scheme of connection to serial port pins for two-axis system