ESP32 DOIT Dev Kit Built-in bluetooth vs HC-05 time to send packets

[wbadry]

Hello,
I was conducting a comparison in terms of speed to send Bluetooth packets using both HC-05 and the built-in Bluetooth.

I was shocked that the legacy HC-05 is 70% faster than the Built-In Bluetooth on ESP32.

Code: [Select all] [Expand/Collapse]

1.  
2.  
3. // LED to toggle when streaming
4. const int LedLight = LED_BUILTIN;
5.  
6. // LED Status (ON-OFF)
7. bool LedStatus = false;
8.  
9. // Start Flag to avoid re-enable timer if it is already on
10. bool StartFlag = false;
11.  
12. // Stop Flag to avoid re-disable timer if it is already off
13. bool StopFlag = false;
14.  
15. // Byte array to hold float conversion
16. byte ByteData[4];
17.  
18. // Sampling time
19. long SamplingTimeInMilliseconds = 10;
20.  
21. // Variable to hold the number of increments needed to change the LED every second
22. int_fast16_t  ChangeLedStatusCount = 0;
23.  
24. // Sample index of EKG, PPG
25. int_fast8_t SampleIndex = 0;
26.  
27. // Flag to be 1 to push new sample
28. volatile bool updateFlag = false;
29.  
30. // Hardware timer
31. hw_timer_t * timer = nullptr;
32.  
33. // Lock for critical section of shared variable (updateFlag)
34. portMUX_TYPE timerMux = portMUX_INITIALIZER_UNLOCKED;
35.  
36. unsigned long tb = 0;
37.  
38. // Change LED Status every 1 second = 10 ms* 100 counts
39. void changeBlinkingLed()
40. {
41.   ChangeLedStatusCount += 1;
42.   if (ChangeLedStatusCount == 100)
43.   {
44.     LedStatus = !(LedStatus);
45.     digitalWrite(LedLight, LedStatus);
46.     ChangeLedStatusCount = 0;
47.   }
48. }
49.  
50. // Convert float number into bytes
51. void float2Bytes(byte ByteData[4], float FloatData)
52. {
53.   memcpy(ByteData, reinterpret_cast<unsigned char*>(&FloatData), 4);
54. }
55.  
56. // Send float as byte array big endian
57. void sendHexData(const float FloatData)
58. {
59.   float2Bytes(ByteData, FloatData);
60.   Serial2.write(ByteData[3]);
61.   Serial2.write(ByteData[2]);
62.   Serial2.write(ByteData[1]);
63.   Serial2.write(ByteData[0]);
64. }
65.  
66. // Packet Header
67. void sendHeader()
68. {
69.   Serial2.write(0xAA);
70.   Serial2.write(0xBB);
71. }
72.  
73. // Send Payload Byte
74. void sendPayload(byte NumberOfChannels)
75. {
76.   const byte Size = NumberOfChannels * 4;
77.   Serial2.write(Size);
78. }
79.  
80.  
81. // On Timer Event
82. void IRAM_ATTR onTimer()
83. {
84.   // Enter critical section
85.   portENTER_CRITICAL_ISR(&timerMux);
86.  
87.   // Set flag
88.   updateFlag = true;
89.  
90.   // Exit critical section
91.   portEXIT_CRITICAL_ISR(&timerMux);
92. }
93.  
94. void setup()
95. {
96.     const uint32_t Freq = 80;
97.     //Set CPU clock to 240 MHz fo example
98.     setCpuFrequencyMhz(Freq);
99.  
100.     // Set Serial2 baudrate
101.     Serial2.begin(115200);
102.  
103.     // LED as output
104.     pinMode(LedLight, OUTPUT);
105.  
106.     /* Use 1st timer of 4 */
107.     /* 1 tick takes 80 MHZ/prescaler (80) = 1us so we set the divider 80 and count up */
108.     timer = timerBegin(0, Freq, true);
109.  
110.     /* Attach onTimer function to our timer */
111.     timerAttachInterrupt(timer, &onTimer, true);
112.  
113.     /* Set alarm to call onTimer function every second 1 tick is 1us
114.       => 1 second is 10000us */
115.     /* Repeat the alarm (third parameter) */
116.     timerAlarmWrite(timer, 10000, true);
117. }
118.  
119.  
120. void loop()
121. {
122.     if (updateFlag == true)
123.     {
124.         changeBlinkingLed();
125.  
126.         tb = micros();
127.         sendHeader();
128.         sendPayload(8);
129.         sendHexData(1.0);
130.         sendHexData(2.0);
131.         sendHexData(3.0);
132.         sendHexData(4.0);
133.         sendHexData(5.0);
134.         sendHexData(6.0);
135.         sendHexData(7.0);
136.         tb = micros() - tb;
137.         sendHexData(tb);
138.        
139.         SampleIndex++;
140.         SampleIndex = (SampleIndex > 99) ? 0 : SampleIndex;
141.  
142.         portENTER_CRITICAL_ISR(&timerMux);
143.         updateFlag = false;
144.         portEXIT_CRITICAL_ISR(&timerMux);
145.     }
146.     if (Serial2.available() > 0)
147.     {
148.         const auto IncomingCommand = Serial2.read();
149.         switch (IncomingCommand)
150.         {
151.         case '*':
152.             if (!StartFlag)
153.             {
154.                 StartFlag = true;
155.                 StopFlag = false;
156.                 /* Start an alarm */
157.                 timerAlarmEnable(timer);
158.             }
159.             break;
160.         case '#':
161.             if (!StopFlag)
162.             {
163.                 StopFlag = true;
164.                 StartFlag = false;
165.                 timerAlarmDisable(timer);
166.             }
167.             break;
168.         default:
169.             Serial2.flush();
170.         }
171.     }
172. }

GeSHi © Codebox Plus Extension

And this is the Built-In Bluetooth

Code: [Select all] [Expand/Collapse]

1. #include "esp32-hal-cpu.h"
2. #include "BluetoothSerial.h"
3.  
4. // Verify Bluetooth is enabled
5. #if !defined(CONFIG_BT_ENABLED) || !defined(CONFIG_BLUEDROID_ENABLED)
6. #error Bluetooth is not enabled! Please run `make menuconfig` to and enable it
7. #endif
8.  
9. // ESP32 header
10. BluetoothSerial SerialBT;
11.  
12. // LED to toggle when streaming
13. const int LedLight = LED_BUILTIN;
14.  
15. // LED Status (ON-OFF)
16. bool LedStatus = false;
17.  
18. // Start Flag to avoid re-enable timer if it is already on
19. bool StartFlag = false;
20.  
21. // Stop Flag to avoid re-disable timer if it is already off
22. bool StopFlag = false;
23.  
24. // Byte array to hold float conversion
25. byte ByteData[4];
26.  
27. // Sampling time
28. long SamplingTimeInMilliseconds = 10;
29.  
30. // Variable to hold the number of increments needed to change the LED every second
31. int_fast16_t  ChangeLedStatusCount = 0;
32.  
33. // Sample index of EKG, PPG
34. int_fast8_t SampleIndex = 0;
35.  
36. // Flag to be 1 to push new sample
37. volatile bool updateFlag = false;
38.  
39. // Hardware timer
40. hw_timer_t * timer = nullptr;
41.  
42. // Lock for critical section of shared variable (updateFlag)
43. portMUX_TYPE timerMux = portMUX_INITIALIZER_UNLOCKED;
44.  
45. // Time to send
46. unsigned long bt = 0.0;
47.  
48. // Change LED Status every 1 second = 10 ms* 100 counts
49. void changeBlinkingLed()
50. {
51.   ChangeLedStatusCount += 1;
52.   if (ChangeLedStatusCount == 100)
53.   {
54.     LedStatus = !(LedStatus);
55.     digitalWrite(LedLight, LedStatus);
56.     ChangeLedStatusCount = 0;
57.   }
58. }
59.  
60. // Convert float number into bytes
61. void float2Bytes(byte ByteData[4], float FloatData)
62. {
63.   memcpy(ByteData, reinterpret_cast<unsigned char*>(&FloatData), 4);
64. }
65.  
66. // Send float as byte array big endian
67. void sendHexData(const float FloatData)
68. {
69.   float2Bytes(ByteData, FloatData);
70.   SerialBT.write(ByteData[3]);
71.   SerialBT.write(ByteData[2]);
72.   SerialBT.write(ByteData[1]);
73.   SerialBT.write(ByteData[0]);
74. }
75.  
76. // Packet Header
77. void sendHeader()
78. {
79.     SerialBT.write(0xAA);
80.     SerialBT.write(0xBB);
81. }
82.  
83. // Send Payload Byte
84. void sendPayload(byte NumberOfChannels)
85. {
86.   const byte Size = NumberOfChannels * 4;
87.   SerialBT.write(Size);
88. }
89.  
90. // On Timer Event
91. void IRAM_ATTR onTimer()
92. {
93.   // Enter critical section
94.   portENTER_CRITICAL_ISR(&timerMux);
95.  
96.   // Set flag
97.   updateFlag = true;
98.  
99.   // Exit critical section
100.   portEXIT_CRITICAL_ISR(&timerMux);
101. }
102.  
103. void setup()
104. {
105.     const uint32_t Freq = 80;
106.     //Set CPU clock to 240 MHz fo example
107.     //setCpuFrequencyMhz(Freq);
108.  
109.     // Set Serial2 baudrate
110.     Serial2.begin(115200);
111.  
112.     // LED as output
113.     pinMode(LedLight, OUTPUT);
114.  
115.     // Populate ESP32 bluetooth name
116.     SerialBT.begin("BT-ESP32"); //Bluetooth device name
117.  
118.     /* Use 1st timer of 4 */
119.     /* 1 tick takes 80 MHZ/prescaler (80) = 1us so we set the divider 80 and count up */
120.     timer = timerBegin(0, Freq, true);
121.  
122.     /* Attach onTimer function to our timer */
123.     timerAttachInterrupt(timer, &onTimer, true);
124.  
125.     /* Set alarm to call onTimer function every second 1 tick is 1us
126.       => 1 second is 10000us */
127.     /* Repeat the alarm (third parameter) */
128.     timerAlarmWrite(timer, 10000, true);
129. }
130.  
131.  
132. void loop()
133. {
134.     if (updateFlag == true)
135.     {
136.         changeBlinkingLed();
137.         bt = micros();
138.        
139.         sendHeader();
140.         sendPayload(8);
141.         sendHexData(1.0);
142.         sendHexData(2.0);
143.         sendHexData(3.0);
144.         sendHexData(4.0);
145.         sendHexData(5.0);
146.         sendHexData(6.0);
147.         sendHexData(7.0);
148.         bt = micros() - bt;
149.         sendHexData(bt);
150.  
151.         SampleIndex++;
152.         SampleIndex = (SampleIndex > 99) ? 0 : SampleIndex;
153.  
154.         portENTER_CRITICAL_ISR(&timerMux);
155.         updateFlag = false;
156.         portEXIT_CRITICAL_ISR(&timerMux);
157.     }
158.     if (SerialBT.available() > 0)
159.     {
160.         const auto IncomingCommand = SerialBT.read();
161.         switch (IncomingCommand)
162.         {
163.         case '*':
164.             if (!StartFlag)
165.             {
166.                 StartFlag = true;
167.                 StopFlag = false;
168.                 /* Start an alarm */
169.                 timerAlarmEnable(timer);
170.             }
171.             break;
172.         case '#':
173.             if (!StopFlag)
174.             {
175.                 StopFlag = true;
176.                 StartFlag = false;
177.                 timerAlarmDisable(timer);
178.             }
179.             break;
180.         default:
181.             SerialBT.flush();
182.         }
183.     }
184. }

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The problem is on HC-05, I am getting an average of 500us, and using the Built-In BT it is 1500us