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185 lines
7.6 KiB
Markdown
185 lines
7.6 KiB
Markdown
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# TWAI Network Example
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(See the README.md file in the upper level 'examples' directory for more information about examples.)
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This example demonstrates how to use the TWAI driver to program a target (ESP32 or ESP32-S2) as a TWAI node, and have the two nodes (Network Master and Network Slave) communicate on a TWAI network. The Listen Only node is optional and acts as a network monitor meaning that it only receives messages and does not influence the bus in any way (i.e. doesn't not acknowledge or send error frames).
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Note that concept of master/slave in this example refers to which node initiates
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and stops the transfer of a stream of data messages.
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## How to use example
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### Hardware Required
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This example requires at least two targets (e.g., an ESP32 or ESP32-S2) to act as the Network Master and Network Slave. The third target (Listen Only) is optional. Each target must be connected to an external transceiver (e.g., a SN65HVD23X transceiver). The transceivers must then be interconnected to form a TWAI network.
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The following diagram illustrates an example network:
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```
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---------- ---------- --------------
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| Master | | Slave | | Listen Only |
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| TX RX | | TX RX | | TX RX |
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---------- ---------- --------------
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---------- ---------- ----------
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| D R | | D R | | D R |
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| VP230 | | VP230 | | VP230 |
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| H L | | H L | | H L |
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---------- ---------- ----------
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|--x------|-----x------|-----x------|--| H
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|---------x------------x------------x--| L
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```
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Note: If you don't have an external transceiver, you can still run the [TWAI Self Test example](../twai_self_test/README.md)
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### Configure the project
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For each node in the TWAI network (i.e., Master, Slave, Listen Only)...
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* Set the target of the build (where `{IDF_TARGET}` stands for the target chip such as `eszp32` or `esp32s2`).
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* Then run `menuconfig` to configure the example.
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```
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idf.py set-target {IDF_TARGET}
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idf.py menuconfig
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```
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* Under `Example Configuration`, configure the pin assignments using the options `TX GPIO Number` and `RX GPIO Number` according to how the target was connected to the transceiver. By default, `TX GPIO Number` and `RX GPIO Number` are set to the following values:
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* On the ESP32, `TX GPIO Number` and `RX GPIO Number` default to `21` and `22` respectively
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* On the ESP32-S2, `TX GPIO Number` and `RX GPIO Number` default to `20` and `21` respectively
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### Build and Flash
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For each node, build the project and flash it to the board, then run monitor tool to view serial output:
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```
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idf.py -p PORT flash monitor
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```
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(Replace PORT with the name of the serial port to use.)
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(To exit the serial monitor, type ``Ctrl-]``.)
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See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
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## Example Output
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Network Master
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```
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I (345) TWAI Master: Driver installed
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I (345) TWAI Master: Driver started
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I (345) TWAI Master: Transmitting ping
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I (3105) TWAI Master: Transmitted start command
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I (3105) TWAI Master: Received data value 339
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...
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I (5545) TWAI Master: Received data value 584
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I (5545) TWAI Master: Transmitted stop command
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I (5595) TWAI Master: Driver stopped
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I (6595) TWAI Master: Driver started
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I (6595) TWAI Master: Transmitting ping
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I (7095) TWAI Master: Transmitted start command
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I (7095) TWAI Master: Received data value 738
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...
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I (9535) TWAI Master: Received data value 983
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I (9535) TWAI Master: Transmitted stop command
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I (9585) TWAI Master: Driver stopped
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I (10585) TWAI Master: Driver started
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I (10585) TWAI Master: Transmitting ping
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I (11085) TWAI Master: Transmitted start command
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I (11085) TWAI Master: Received data value 1137
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...
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I (13525) TWAI Master: Received data value 1382
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I (13525) TWAI Master: Transmitted stop command
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I (13575) TWAI Master: Driver stopped
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I (14575) TWAI Master: Driver uninstalled
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```
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Network Slave
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```
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Slave starting in 3
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Slave starting in 2
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Slave starting in 1
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I (6322) TWAI Slave: Driver installed
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I (6322) TWAI Slave: Driver started
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I (6462) TWAI Slave: Transmitted ping response
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I (6712) TWAI Slave: Start transmitting data
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I (6712) TWAI Slave: Transmitted data value 339
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...
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I (9162) TWAI Slave: Transmitted data value 584
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I (9212) TWAI Slave: Transmitted stop response
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I (9312) TWAI Slave: Driver stopped
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I (10312) TWAI Slave: Driver started
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I (10452) TWAI Slave: Transmitted ping response
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I (10702) TWAI Slave: Start transmitting data
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I (10702) TWAI Slave: Transmitted data value 738
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...
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I (13152) TWAI Slave: Transmitted data value 983
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I (13202) TWAI Slave: Transmitted stop response
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I (13302) TWAI Slave: Driver stopped
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I (14302) TWAI Slave: Driver started
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I (14442) TWAI Slave: Transmitted ping response
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I (14692) TWAI Slave: Start transmitting data
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I (14692) TWAI Slave: Transmitted data value 1137
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...
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I (17142) TWAI Slave: Transmitted data value 1382
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I (17192) TWAI Slave: Transmitted stop response
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I (17292) TWAI Slave: Driver stopped
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I (18292) TWAI Slave: Driver uninstalled
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```
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Network Listen Only
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```
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I (326) TWAI Listen Only: Driver installed
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I (326) TWAI Listen Only: Driver started
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I (366) TWAI Listen Only: Received master ping
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...
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I (1866) TWAI Listen Only: Received master ping
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I (1866) TWAI Listen Only: Received slave ping response
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I (2116) TWAI Listen Only: Received master start command
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I (2116) TWAI Listen Only: Received data value 329
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...
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I (4566) TWAI Listen Only: Received data value 574
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I (4566) TWAI Listen Only: Received master stop command
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I (4606) TWAI Listen Only: Received slave stop response
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I (5606) TWAI Listen Only: Received master ping
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I (5856) TWAI Listen Only: Received master ping
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I (5856) TWAI Listen Only: Received slave ping response
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I (6106) TWAI Listen Only: Received master start command
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I (6106) TWAI Listen Only: Received data value 728
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...
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I (8556) TWAI Listen Only: Received data value 973
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I (8556) TWAI Listen Only: Received master stop command
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I (8596) TWAI Listen Only: Received slave stop response
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I (9596) TWAI Listen Only: Received master ping
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I (9846) TWAI Listen Only: Received master ping
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I (9846) TWAI Listen Only: Received slave ping response
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I (10096) TWAI Listen Only: Received master start command
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I (10096) TWAI Listen Only: Received data value 1127
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...
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I (12546) TWAI Listen Only: Received data value 1372
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I (12546) TWAI Listen Only: Received master stop command
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I (12586) TWAI Listen Only: Received slave stop response
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I (12586) TWAI Listen Only: Driver stopped
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I (12586) TWAI Listen Only: Driver uninstalled
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```
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## Example Breakdown
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The communication between the Network Master and Network Slave execute the following steps over multiple iterations:
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1. Both master and slave go through install and start their TWAI drivers independently.
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2. The master repeatedly sends **PING** messages until it receives a **PING_RESP** (ping response message) from the slave. The slave will only send a **PING_RESP** message when it receives a **PING** message from the master.
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3. Once the master has received the **PING_RESP** from the slave, it will send a **START_CMD** message to the slave.
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4. Upon receiving the **START_CMD** message, the slave will start transmitting **DATA** messages until the master sends a **STOP_CMD**. The master will send the **STOP_CMD** after receiving N **DATA** messages from the slave (N = 50 by default).
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5. When the slave receives the **STOP_CMD**, it will confirm that it has stopped by sending a **STOP_RESP** message to the master.
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