From b643a09188172cd62980eccafa37cbeb65736202 Mon Sep 17 00:00:00 2001
From: Sam Perry <17242713+sdp8483@users.noreply.github.com>
Date: Fri, 23 Dec 2022 17:43:53 -0500
Subject: [PATCH] add comments

---
 .../esp32can_receive/esp32can_receive.ino     | 18 +++++++++++++----
 examples/esp32can_send/esp32can_send.ino      | 20 +++++++++++++++----
 2 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/examples/esp32can_receive/esp32can_receive.ino b/examples/esp32can_receive/esp32can_receive.ino
index d533ee8..d829f33 100644
--- a/examples/esp32can_receive/esp32can_receive.ino
+++ b/examples/esp32can_receive/esp32can_receive.ino
@@ -1,3 +1,12 @@
+/* ESP32 Arduino CAN Receive Basic Demo
+ *     This example will receive messages on the CAN bus
+ *
+ *     An external transceiver is required and should be connected 
+ *     to the CAN_tx and CAN_rx gpio pins specified by CANInit. Be sure
+ *     to use a 3.3V compatable transceiver such as the SN65HVD23x
+ *
+ */
+
 #include <Arduino.h>
 #include <ESP32CAN.h>
 
@@ -5,18 +14,19 @@ void setup() {
   Serial.begin(115200);
   Serial.println("ESP32-Arduino-CAN Receive Basic Demo");
 
+  /* initialize and start, use pin 5 as CAN_tx and pin 4 as CAN_rx, CAN bus is set to 500kbps */
   ESP32Can.CANInit(GPIO_NUM_5, GPIO_NUM_4, ESP32CAN_SPEED_500KBPS);
 }
 
 void loop() {
   twai_message_t rx_frame;
   
-  if (ESP32CAN_OK == ESP32Can.CANReadFrame(&rx_frame)) {  /* CAN message received*/
-    Serial.print(rx_frame.identifier, HEX);
+  if (ESP32CAN_OK == ESP32Can.CANReadFrame(&rx_frame)) {  /* only print when CAN message is received*/
+    Serial.print(rx_frame.identifier, HEX);               /* print the CAN ID*/
     Serial.print(" ");
-    Serial.print(rx_frame.data_length_code);
+    Serial.print(rx_frame.data_length_code);              /* print number of bytes in data frame*/
     
-    for (int i=0; i<rx_frame.data_length_code; i++) {
+    for (int i=0; i<rx_frame.data_length_code; i++) {     /* print the data frame*/
       Serial.print(rx_frame.data[i], HEX);
     }
 
diff --git a/examples/esp32can_send/esp32can_send.ino b/examples/esp32can_send/esp32can_send.ino
index e59dbad..c71ca92 100644
--- a/examples/esp32can_send/esp32can_send.ino
+++ b/examples/esp32can_send/esp32can_send.ino
@@ -1,3 +1,12 @@
+/* ESP32 Arduino CAN Send Basic Demo
+ *     This example will send messages on the CAN bus
+ *
+ *     An external transceiver is required and should be connected 
+ *     to the CAN_tx and CAN_rx gpio pins specified by CANInit. Be sure
+ *     to use a 3.3V compatable transceiver such as the SN65HVD23x
+ *
+ */
+
 #include <Arduino.h>
 #include <ESP32CAN.h>
 
@@ -5,16 +14,18 @@ void setup() {
   Serial.begin(115200);
   Serial.println("ESP32-Arduino-CAN Send Basic Demo");
 
+  /* initialize and start, use pin 5 as CAN_tx and pin 4 as CAN_rx, CAN bus is set to 500kbps */
   ESP32Can.CANInit(GPIO_NUM_5, GPIO_NUM_4, ESP32_SPEED_500KBPS);
 }
 
 void loop() {
   twai_message_t tx_frame;
   
-  tx_frame.extd = 0;
-  tx_frame.data_length_code = 8;
-  tx_frame.identifier = 0x123;
+  tx_frame.extd = 0;              /* CAN ID is standard 11bit, for 29bit set to 1*/
+  tx_frame.data_length_code = 8;  /* send 8 bytes of data */
+  tx_frame.identifier = 0x123;    /* CAN id is 0x123 */
 
+  /* assemble the 8 bytes of data */
   tx_frame.data[0] = 0xDE;
   tx_frame.data[1] = 0xAD;
   tx_frame.data[2] = 0xBE;
@@ -24,9 +35,10 @@ void loop() {
   tx_frame.data[6] = 0xBA;
   tx_frame.data[7] = 0x11;
 
-  ESP32Can.CANWriteFrame(&tx_frame);
+  ESP32Can.CANWriteFrame(&tx_frame); /* send the CAN message */
 
   Serial.println("CAN Frame Sent");
 
+  /* delay before sending another CAN message*/
   delay(1000);
 }