CAN/RS232 Shield

The CAN/RS232 Shield combines a CAN-FD transceiver with an RS-232 transceiver so the OpenMV Cam can talk to vehicles, controllers, and legacy serial gear from a single shield, with wide-input power and reverse-voltage protection.

CAN/RS232 Shield

For full datasheet, photos, and ordering see the CAN/RS232 Shield product page.

Highlights

  • 8 Mb/s CAN-FD with on-board termination and filtering

  • 1 Mb/s RS-232 with integrated filtering

  • 6-36 V input, reverse-voltage tolerant

  • 0-5 V ADC input with ±36 V overvoltage protection

  • 0-5 V digital I/O for camera-sync triggers, short-circuit protected

Pinout

CAN/RS232 Shield Pinout

Pin reference

Pin

Function

P1

CAN TX (default)

P2

CAN TX (alternative — selectable via solder bridge)

P3

CAN RX

P4

RS-232 TX → drives the line out

P5

RS-232 RX ← receives line in

P6

Level-shifted AIN readback (0–3.3 V on P6)

P10

SYN — open-drain digital I/O on the terminal block

PWR in

6–36 V wide input on the terminal block (reverse-voltage tolerant)

AIN in

Analog input on the terminal block

VIN out

5.4 V at up to 600 mA from the on-board regulator

3.3V rail

Powers the shield’s on-board electronics

GND rail

Common ground

Note

AIN is overvoltage-protected up to ±36 V and defaults to a 0–5 V voltage input, scaled down to 0–3.3 V on P6. Bridge the 4–20 mA mode shunt on the back of the shield to switch AIN to a 4–20 mA current-loop input.

Note

SYN is an open-drain digital line, pulled up to 3.3 V on the camera side and 5 V on the SYN terminal side. By default it’s an input — the shield level-shifts 0–5 V on SYN down to 0–3.3 V on P10. Change the on-board solder jumper to flip P10 into an output, level-shifting 0–3.3 V on P10 up to 0–5 V on SYN.

Usage

Send and receive CAN-FD frames on P1 (TX) / P3 (RX):

from machine import CAN

can = CAN(1, 1_000_000)
can.send([0xDE, 0xAD, 0xBE, 0xEF], 0x123)
print(can.recv())

Echo bytes over RS-232 on P4 (TX) / P5 (RX):

from machine import UART

uart = UART(3, baudrate=115200)
uart.write("hello\n")
print(uart.read())

Read the AIN terminal-block input through the level-shifted P6 pin:

from machine import ADC
import time

ain = ADC("P6")

while True:
    v = ain.read_u16() * 3.3 / 65535
    print("AIN:", v * (5.0 / 3.3), "V")
    time.sleep_ms(100)

React to a falling edge on the SYN line — for example, to sync the camera with another device pulling SYN low:

from machine import Pin

def on_sync(pin):
    print("SYN falling edge")

syn = Pin("P10", Pin.IN)
syn.irq(on_sync, Pin.IRQ_FALLING)

Warning

This page is under construction.