Product Specifications

Mode 4: Packetized Serial Mode
Packetized Serial uses TTL level multi-byte serial commands to set the motor speed and
direction. Packetized serial is a one-direction only interface. The transmit line from the host is
connected to S1. The host’s receive line is not connected to the Sabertooth. Because of this,
multiple Sabertooth 2x10 motor drivers can be connected to the same serial transmitter. It is also
possible to use SyRen and Sabertooth motor drivers together from the same serial source, as well
as any other serial device, as long as it will not act on the packets sent to the Sabertooth. If using
a true RS-232 device like a PC’s serial port, it is necessary to use a level converter to shift the –
10V to 10V rs-232 levels to the 0v-5v TTL. Packetized serial uses an address byte to select the
target device. The baud rate is selected automatically by sending the bauding character (170 in
decimal, AA in hex) before any commands are sent.
Packet Overview
The packet format for the Sabertooth consists of an address byte, a command byte, a data byte
and a seven bit checksum. Address bytes have value greater than 128, and all subsequent bytes
have values 127 or lower. This allows multiple types of devices to share the same serial line.
An example packet and pseudo-code to generate it are shown in Figures 7.1 and 7.2
Packet
Address: 130
Command : 0
Data: 64
Checksum: 66
Void DriveForward(char address, char speed)
{
Putc(address);
Putc(0);
Putc(speed);
Putc((address + 0 + speed) & 0b01111111);
}
Figure 7.1: Example 50% forward Figure 7.2: Pseudocode to generate 7.1
Baud Rate Selection:
Packetized Serial operates with an 8N1 protocol – 8 data bytes, no parity bits and one stop bit.
The baud rate is automatically calculated by the first character sent. This character must be (170
in decimal) (binary 10101010) and must be sent before any serial communications are done. It is
not possible to change the baud rate once the bauding character has been sent. The valid baud
rates are 2400, 9600, 19200 and 38400 baud. Until the bauding character is sent, the driver will
accept no commands and blue status LED will stay lit. Please note that Sabertooth may take up
to a second to start up after power is applied, depending on the power source being used.
Sending the bauding character during this time period may cause undesirable results. When
using Packetized Serial mode, please allow a two-second delay between applying power and
sending the bauding character to the drivers.