TWAI Transmit Issue, When 2 Bytes of the Data are variable numbers. Going crazy here

[Ravenholem]

Hello,
I have been pulling my hair out with this issue.. Seriously doesn't make any sense what so ever to me.
When I try to have two bytes of the Data[] Array be operated on the whole Twai Transmit function breaks.
Look at the below code I made a comment of where the issue happens.
This is what goes on,

Scenario 1:
RPM is a incrementing variable so always different
Data[2] = PRM; // RPM is 16bit so by doing this we get LSB
Data[3] = PRM >> 8; // Shift 8 give me the higher MSB
Results: Will get a few packets on the receiving end (Another ESP32) then start seeing 0x107 (Que Full on the sending unit)

Scenario 2:
RPM is a incrementing variable so always different
Data[2] = 43; // Just random fixed number at compile time
Data[3] = PRM >> 8; // Shift 8 give me the higher MSB
Results: Receiving unit will ACK and recive every single packet sent for as long as both devices are on and everything works normal.

Scenario 3:
Even stranger
Data[2] = PRM; // RPM is 16bit so by doing this we get LSB
Data[3] = PRM // RPM is 16bit so by doing this we get LSB
Results: Same as Scenario 1... Will get a few packets on the receiving end (Another ESP32) then start seeing 0x107 (Que Full on the sending unit)

If anyone has any insight on this please help me, I can't make heads or tails out of any of this. Because it's a basic operation that causes all this... I have no understanding of how doing any of this would cause the Twai Transmit function to start Que Full Error triggering.

Thank you

Exact Code I have compiled and running right now... I get 3 or 4 Packets ACK and showing up on the Receiving esp32, then the transmitting ESP32 just starts saying Error 0x107 (Transmit Que Full)

Code: [Select all] [Expand/Collapse]

1. #include <stdio.h>
2. #include "sdkconfig.h"  // ADDED 9/7
3. #include "string.h"
4. #include "freertos/FreeRTOS.h"
5. #include "freertos/task.h"
6. #include "freertos/queue.h"
7. #include "esp_attr.h"
8. #include "soc/rtc.h"
9. // CAN_BUS
10. #include "driver/twai.h"
11. // I/O
12. #include "driver/gpio.h"
13.  
14.  
15. void Init_CAN(){
16.    //Initialize configuration structures using macro initializers
17.     twai_general_config_t g_config = TWAI_GENERAL_CONFIG_DEFAULT(GPIO_NUM_21, GPIO_NUM_22, TWAI_MODE_NORMAL);
18.     g_config.intr_flags = ESP_INTR_FLAG_IRAM;
19.     twai_timing_config_t t_config = TWAI_TIMING_CONFIG_500KBITS();
20.     twai_filter_config_t f_config = TWAI_FILTER_CONFIG_ACCEPT_ALL();
21.  
22.     //Install CAN driver
23.     if (twai_driver_install(&g_config, &t_config, &f_config) == ESP_OK) {
24.         printf("Driver installed\n");
25.     } else {
26.         printf("Failed to install driver\n");
27.         return;
28.     }
29.  
30.     //Start CAN driver
31.     if (twai_start() == ESP_OK) {
32.         printf("Driver started\n");
33.     } else {
34.         printf("Failed to start driver\n");
35.         return;
36.     }
37. }
38.  
39. // CAN BUS Transmiit
40. void CAN_Transmit(void *arg){
41.     static uint32_t Msgs_sent = 0;
42.     uint8_t Ticker = 0; // Used as a simple timer
43.     uint16_t RPM = 0;   // Increments during each tick to simulate RPM rise
44.     uint16_t ret = 0;   // Holds the error coming back from Twai que
45.    
46.     //Configure message to transmit
47.     twai_message_t message = {.flags = 0, .data_length_code = 8, .identifier = 0x742, .data = {0, 0, 0, 0, 0, 0, 0, 0}};
48.    
49.     while(true){ // infinite loop
50.  
51.         if(Ticker == 100){
52.             message.identifier = 0x315;
53.             /*
54.              *  This is the problem area, if you change RPM >> 8 to a fixed number then all CAN TX transmits work
55.              *   If you leave it as it is a few Frames will get ACK and then you start seeing Transmit Que Full Errors
56.              */
57.             message.data[2] = (uint8_t) RPM;      // RPM "I even type cast here"
58.             message.data[3] = RPM >> 8;             // RPM
59.             if((ret = twai_transmit(&message,  0)) == ESP_OK) {
60.                 printf("S\n");
61.             }else{
62.                 printf("%x\n", ret);
63.             }
64.             Ticker++;
65.         }else if(Ticker == 200){
66.             // Gear and Mode
67.             message.identifier = 0x232;
68.             message.data[3] = 3;         // Just other Testing
69.             message.data[5] = 0xE0;   // Just other Testing
70.             if(twai_transmit(&message, 0) == ESP_OK) {        
71.                 printf("G\n");    
72.             }
73.             Ticker = 0;
74.         }else{
75.             Ticker++;
76.         }
77.  
78.         // Pause the task for 500ms
79.         if(RPM > 9000){
80.             RPM = 0;
81.         }else{
82.             RPM++;
83.         }
84.  
85.         // ets_delay_us(100);
86.         vTaskDelay(11 / portTICK_PERIOD_MS);  
87.     }
88. }
89.  
90.  
91. // CAN BUS Reciving
92. void CAN_RX(void *arg){
93.     //Wait for message to be received
94.     while (1)
95.     {
96.         twai_message_t message;
97.         if (twai_receive(&message, pdMS_TO_TICKS(1)) == ESP_OK) {
98.             printf("Message received\n");
99.             //Process received message
100.             if (message.extd) {
101.                 printf("Message is in Extended Format\n");
102.             } else {
103.                 printf("Message is in Standard Format\n");
104.             }
105.    
106.             printf("ID is %x\n", message.identifier);
107.    
108.             if (!(message.rtr)) {
109.                 for (int i = 0; i < message.data_length_code; i++) {
110.                     printf("Data byte %d = %d\n", i, message.data[i]);
111.                 }
112.             }
113.         } else {
114.         //  printf("Failed to receive message\n");
115.         //  return 0;
116.         }
117.        
118.         vTaskDelay(500 / portTICK_PERIOD_MS);
119.     }
120.  
121. }
122.  
123.  
124. void app_main(void)
125. {
126.  
127.     Init_CAN();
128.     xTaskCreate(CAN_Transmit, "CAN_TX", 10000, NULL, 5, NULL);
129. //    xTaskCreate(CAN_RX, "CAN_RX", 10000, NULL, 4, NULL); // Not doing any RX this sends only
130.    
131.  
132. }

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