2020-04-09 04:40:57 -04:00
|
|
|
| Supported Targets | ESP32 |
|
|
|
|
|
| ----------------- | ----- |
|
|
|
|
|
|
2017-12-18 07:32:29 -05:00
|
|
|
# CAN Self Test Example
|
|
|
|
|
|
|
|
|
|
## Overview
|
|
|
|
|
The CAN Self Test Example demonstrates the self testing capabilities of the
|
|
|
|
|
ESP32 CAN peripheral and **only requires a single ESP32 module to run**.
|
|
|
|
|
The Self Test Example can be used to verify that the wiring between the ESP32
|
|
|
|
|
and an external transceiver operates correctly.
|
|
|
|
|
|
|
|
|
|
The CAN Self Test Example will do the following over multiple iterations:
|
|
|
|
|
|
|
|
|
|
1. Start the CAN driver
|
|
|
|
|
2. Simultaneously transmit and receive messages using the self reception request.
|
|
|
|
|
3. Stop the CAN driver
|
|
|
|
|
|
|
|
|
|
## External Transceiver and Pin Assignment
|
|
|
|
|
The CAN controller in the ESP32 **does not contain an internal transceiver**.
|
|
|
|
|
Therefore users are responsible for providing an external transceiver compatible
|
|
|
|
|
with the physical layer specifications of their target ISO standard (such as
|
|
|
|
|
SN65HVD23X transceivers for ISO 11898-2 compatibility)
|
|
|
|
|
|
|
|
|
|
The CAN controller in the ESP32 represents dominant bits to the transceiver as
|
|
|
|
|
logic low, and recessive bits as logic high. The Self Test Example utilizes the
|
|
|
|
|
following default pin assignments
|
|
|
|
|
|
|
|
|
|
* TX Pin is routed to GPIO21
|
|
|
|
|
* RX Pin is routed to GPIO22
|
|
|
|
|
|
|
|
|
|
## Note
|
|
|
|
|
If the Self Test Example does not receive any messages, it is likely that the
|
|
|
|
|
wiring between the ESP32 and the external transceiver is incorrect. To verify
|
|
|
|
|
that the CAN controller in the ESP32 is operating correctly, users can bypass
|
|
|
|
|
the external transceiver by connecting the TX Pin directly to the RX Pin when
|
|
|
|
|
running the Self Test Example.
|
