VEXBridge is a custom PCB designed by VEX-U team DevilBots to easily interface 3rd-party components such as a Raspberry Pi, Arduino, or Jetson Nano with a VEX V5 brain. It includes a 5V regulator, UART bridge, and status LEDs for PWR/RX/TX. Its made and designed in KiCAD which is a free and open source software for designing electrical PCBs.
For voltage regulation, the bridge integrates a LM2596S. This steps the fluctuating 12V rail from the VEX battery down to a stable 5V (3A max). While this isn't designed to drive DC motors, it should be enough to power typical SBCs.
For communication, the bridge uses a MAX485 to convert the RS-485 signal from the VEX Brain to UART which is used by common SBCs. Unfortunately, this connection is only half-duplex. By default, the RTS pin is pulled low which disables transmission and enables receiving. In order to start transmitting data to the VEX brain, the RTS pin must be pulled high. This can be done directly with the SBC GPIO or using the ADI pins on the VEX brain.
PROS provides an conveniently built-in Serial object to communicate directly w/ the V5 port.
uint8_t PORT = 1;
uint32_t BAUDRATE = 115200;
pros::Serial m_bridge = pros::Serial(PORT, BAUDRATE);
// Transmit
uint8_t buffer[] = {0x01, 0x02, 0x03};
m_bridge.write(buffer, sizeof(buffer));
// Receive
while (m_bridge.get_read_avail())
printf("Read: %d\n", serial.read_byte());
// See PROS documentation/implementation for more details
// https://github.com/purduesigbots/pros/blob/develop-pros-4/include/pros/serial.hppWhen writing data, it should be encoded w/ COBS to provide data checksum and mark packet beginning/end.