CAN Shield#

The CAN Shield gives the OpenMV Cam a CAN-bus link via a DB9 connector, with an on-board 12 V to 5 V regulator so the shield can power the camera from a vehicle bus.

CAN Shield

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

Note

Not supported on the OpenMV Cam RT1062.

Highlights#

  • CAN bus up to 1 Mb/s

  • On-board 12 V to 5 V regulator

Pinout#

CAN Shield Pinout

Pin reference#

Pin

Function

P2

CAN TX

P3

CAN RX

P6

CAN standby (optional — see note)

PWR in

12 V vehicle-bus input on the DB9 connector

VIN out

5 V regulator output (powers the camera)

3.3V rail

Powers the SN65HVD230 logic

GND rail

Common ground

Note

The SN65HVD230’s standby line is disconnected from P6 by default. Connect the on-board solder bridge to tie it to P6, then drive P6 high to put the transceiver into listen-only standby mode (low keeps it in normal transmit-and-receive mode).

Note

CANL, CANH, VIN, and GND from the DB9 connector are also broken out to through-hole pads on the bottom of the shield — solder wires there if you want to skip the DB9 entirely.

Note

The DB9 pinout can be changed between the standard DB9 CAN layout and the OBD-II layout by changing the three solder-bridge jumpers on the bottom of the shield.

Note

The on-board 120-ohm termination resistor is connected by default. It can be disabled via a solder bridge on the bottom of the shield for buses that already have termination elsewhere.

Usage#

Note

The CAN(1) peripheral number below follows the STM32 mapping. On another processor the bus wired to these pins may be different — check your board’s reference.

Send and receive frames on the CAN bus at 1 Mb/s:

from machine import CAN
import time

can = CAN(2, 1_000_000)
can.set_filters(None)

can.send(0x123, b"\xDE\xAD\xBE\xEF")
print(can.recv())

With the on-board solder bridge connected, drive P6 high to put the SN65HVD230 into listen-only standby mode (low returns it to normal transmit-and-receive):

from machine import Pin
Pin("P6", Pin.OUT).value(1)  # listen-only standby