Example Path: examples/PlatformSpecific/MODRT1171/CAN/CanFdSimple

Overview

This example turns the MODRT1171 into an interactive CAN FD node on FlexCAN1, the module's primary CAN bus. CAN FD (Flexible Data-rate) extends classic CAN with payloads up to 64 bytes per frame and, with bit-rate switching (BRS), a data phase that runs faster than the arbitration phase. This node arbitrates at 500 kbit/s and switches to 2 Mbit/s for the data phase of BRS frames.

A receive task prints every frame seen on the bus – classic or FD – with the FD flags decoded (EDL = FD frame, BRS = bit-rate switch, ESI = error state indicator), and a serial menu sends classic frames, FD frames with BRS, and FD frames without BRS, so you can watch each variant on a bus analyzer or a second node.

An FD node receives and transmits classic frames as well – one FD message buffer carries both types – so this example doubles as a general bus monitor. Every node on a bus carrying FD frames should be FD-capable.

The FlexCAN driver (fsl_flexcan, NXP SDK version 2.11.6) is built into the NetBurner MODRT1171 platform library; the example includes <fsl_flexcan.h> directly and bundles no driver source.

Hardware requirements

MODRT1171 module
CAN FD capable 3.3 V transceiver (MCP2562FD, TJA1051T or similar – it must support the 2 Mbit/s data phase) wired to the FlexCAN1 pins
A second FD-capable CAN node – another MODRT1171 running this example, a USB CAN-FD adapter on a PC, or any other node – configured for 500 kbit/s arbitration / 2 Mbit/s data
Personal Computer
Serial terminal program connected to the MODRT1171 UART0 serial port

Board settings

Wire the FlexCAN1 signals to your transceiver's TXD/RXD pins:

Signal	Module pin (rev 1.5)	Transceiver pin
FlexCAN1 RX	P1.26	RXD
FlexCAN1 TX	P1.27	TXD

Connect the transceiver's CANH/CANL to the bus, and remember the 120 ohm termination resistors at both ends of the bus.

Note: This example is written for the MODRT1171 rev 1.5 module. At rev 1.6 (which makes the module a MOD5441X drop-in replacement), the FlexCAN1 signals move from the P1 header to the P2 header: RX moves P1.26 -> P2.41 and TX moves P1.27 -> P2.44. The FlexCAN1 peripheral instance and this example's driver code are unchanged; only the two pin-function lines in UserMain() change with the module revision. Designs that need more than one CAN bus have options beyond FlexCAN1: FlexCAN3 is available on the I2C pins for designs that do not use I2C (or that bit-bang I2C on spare GPIO), and on rev 1.5 FlexCAN2 also reaches module pins – all three controllers support CAN FD. For pin details see the MODRT1171 Software Developer Guide and the MODRT1171 Pinout Update document: https://www.netburner.com/download/MODRT1171_Rev1p5_to_Rev1p6_Pinout_Update/

Running the demo

Build and load the application, then open the serial terminal:

CAN FD bus: FlexCAN1, 500 kbit/s arbitration / 2000 kbit/s data (BRS),
RX pin P1.26, TX pin P1.27
 
Menu:
  S - send a classic 8-byte frame, ID 0x123
  F - send a 64-byte CAN FD frame with BRS, ID 0x123
  D - send a 64-byte CAN FD frame without BRS, ID 0x123
  T - print the transmit / receive error counters
  A - abort a pending (unacknowledged) transmission
 
Received frames print as they arrive.

Press 'S', 'F', or 'D' to transmit; frames from other nodes print as they arrive, with the frame type decoded:

Received classic ID 0x123 len 8 [50,49,4E,47,38,42,59,54,:PING8BYT]

Received FD+BRS ID 0x123 len 64 [4E,65,74,42,75,72,...:NetBurner MODRT1171 CAN FD...]

A CAN transmission is only complete once another node acknowledges it. If you press a send key with no transceiver or second node attached, the controller keeps retransmitting the frame, the transmit buffer stays busy, and further sends are refused with an explanatory message – press 'A' to abort the pending frame, and 'T' to watch the error counters. The CanErrorMonitor example explores the error states in depth.

To verify CAN FD operation on a single module with no external hardware – including a measured classic-vs-FD throughput comparison – run the CanFdLoopback example first. For the classic CAN version of this node, see CanSimple.