Toradex Apalis Series - 2.17 CAN

Apalis Carrier Board Design Guide
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2.16.1 SPI Signals
A SPI bus consists of one master and one or many slaves. In the Apalis standard, the module is the
SPI master. Some modules may also allow themselves to be used as SPI slaves. Some modules may
provide this function on different, non-standard pins.
Apalis
Pin
Apalis
Signal Name
I/O
Type
Power
Rail
Description
225
SPI1_MOSI
O
CMOS
3.3V
Master Output, Slave Input
223
SPI1_MISO
I
CMOS
3.3V
Master Input, Slave Output
227
SPI1_CS
O
CMOS
3.3V
Slave Select
221
SPI1_CLK
O
CMOS
3.3V
Serial Clock
231
SPI2_MOSI
O
CMOS
3.3V
Master Output, Slave Input
229
SPI2_MISO
I
CMOS
3.3V
Master Input, Slave Output
233
SPI2_CS
O
CMOS
3.3V
Slave Select
235
SPI2_CLK
O
CMOS
3.3V
Serial Clock
Table 28: SPI Signals
2.16.2 Unused SPI Signal Termination
Unused SPI signals can be left unconnected.
2.17 CAN
The controller area network (CAN) bus is a multi-master serial bus standard. It was first introduced
for the automotive sector and soon became widely adopted in the industrial sector. Different
versions of CAN specifications are available. Make sure that the corresponding Apalis module
complies with the required version.
2.17.1 CAN Signals
Apalis
Pin
Apalis
Signal Name
I/O
Type
Power
Rail
Description
14
CAN1_TX
O
CMOS
3.3V
CAN port 1 transmit pin
12
CAN1_RX
I
CMOS
3.3V
CAN port 1 receive pin
18
CAN2_TX
O
CMOS
3.3V
CAN port 2 transmit pin
16
CAN2_RX
I
CMOS
3.3V
CAN port 2 receive pin
Table 29: CAN Signals
2.17.2 Reference Schematics
The CAN interface requires a transceiver on the carrier board. Normally, the CAN interface needs
to be galvanically isolated from the Apalis computer module. There are transceivers with integrated
signal isolation coupler and isolated DC/DC converters available (for example the Analog Devices
ADM3053). The other solution is to use separate components for the transceiver, signal coupler
and DC/DC converter. There are different type of connectors used for the CAN interface. The
reference schematic below uses a DE-9 connector. Since this is not an official standard, some
devices might have a different pin-out.