BluetoothSerial silently drops bytes to be sent

[gohai]

I am using the BluetoothSerial::write() method to send single bytes to the host computer. I have discovered that when I am sending more that ~ 32 bytes at a time, the ESP will silently drop the additional bytes. Adding a delay(10); after each byte fixes this for me, but this is only a stop-gap solution.

Oddly, esp_spp_write does return ESP_OK even when it is dropping bytes, so I believe there is a real bug here.

I am running arduino-esp32 at c63d746, with an rebuilt libbt.a that has a COD set so that macOS will accept the SPP device (but no other changes).

[gohai]

Pinging @copercini

[lyusupov]

@gohai:

when I am sending more that ~ 32 bytes at a time, the ESP will silently drop the additional bytes

could you, please, double check ?

I am sending NMEA strings over SPP (> 32 bytes) and everything is fine to me with current Core ( IDF aaf1239 ).

[gohai]

@lyusupov

I'll double check tomorrow - but I am very certain that I saw it with the previous core (before aaf1239) yesterday.

I saw this using the Firmata library, which uses BluetoothSerial::write(uint8_t), to transmit large ("SYSEX") messages. Logging all the bytes that are passed through write on the UART, I saw all of them - but on the receiver-side I was missing bytes > ~ 37. Oddly, esp_spp_write always returned ESP_OK still. And this started working when I added a delay(10); after each byte sent out.

So, my guess is that there is a certain limit of outstanding bytes to be transmitted over SPP. Perhaps your connection was stronger, so there was less of a backlog? Or perhaps it matters whether you queue multiple bytes at once, or one-by-one (which was what this Firmata library was doing).

[gohai]

@lyusupov

I just double checked with the new core - still seeing this issue!

[copercini]

@gohai do you have some code that I can reproduce this issue here?

[gohai]

Sure - this demonstrates it clearly

#include "BluetoothSerial.h"
BluetoothSerial SerialBT;
static uint32_t last_send = 0;

void setup() {
  SerialBT.begin("ESP32test");
}

void loop() {
  uint32_t now = millis();

  if (SerialBT.hasClient()) {
    if (5000 < now-last_send) {
      for (uint8_t i=0; i < 52; i++) {
        SerialBT.write('A'+(i % 26));
      }
      last_send = now;
    }
  }

  delay(1);
}

This is what I received (I added line breaks to increase readability):

A
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTU
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ATUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRST
ABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZ

[lyusupov]

I can confirm that:

$ time cat /dev/rfcomm0
DEABCFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ
ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ

[copercini]

I can confirm too, it's triggering ESP_SPP_CONG_EVT sometimes that is a congestion event

[I][BluetoothSerial.cpp:59] esp_spp_cb(): ESP_SPP_INIT_EVT
[I][BluetoothSerial.cpp:74] esp_spp_cb(): ESP_SPP_START_EVT
[I][BluetoothSerial.cpp:99] esp_spp_cb(): ESP_SPP_SRV_OPEN_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT
[V][BluetoothSerial.cpp:95] esp_spp_cb(): ESP_SPP_WRITE_EVT

[beegee-tokyo]

I have a project where we (crazy as we are) try to send a short message like 89534,65200 every 5 ms over BluetoothSerial to a terminal. The result is many many many lost messages.
My problem is not the lost messages, but that BTSerial.write() does NOT report any error about it!
I can live with the problem and pause sending or resend data if I only would know that the error occured.

I made a small test sketch were I start sending every 100ms, then every 66ms and so on down to every 5ms. Here is the log result:

ets Jun  8 2016 00:22:57

rst:0x10 (RTCWDT_RTC_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:2
load:0x3fff0018,len:4
load:0x3fff001c,len:812
load:0x40078000,len:0
load:0x40078000,len:11584
entry 0x40078a60

Jul  4 2018 16:09:03
Version: 0.0.1

Sending raw data continously

initBlueTooth()
initBLE()
[D][BLEDevice.cpp:430] setPower(): >> setPower: 7
[D][BLEDevice.cpp:435] setPower(): << setPower
Bluetooth MAC: 24:0A:C4:81:CE:9E
Bluetooth Serial initialized
[I][BluetoothSerial.cpp:59] esp_spp_cb(): ESP_SPP_INIT_EVT
[I][BluetoothSerial.cpp:74] esp_spp_cb(): ESP_SPP_START_EVT
btSppTask loop started
Start with sps of 10
[I][BluetoothSerial.cpp:99] esp_spp_cb(): ESP_SPP_SRV_OPEN_EVT
Switched to sps of 20
Switched to sps of 40
Switched to sps of 50
Switched to sps of 66
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
Switched to sps of 100
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
Switched to sps of 200
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
Switched to sps of 10
[I][BluetoothSerial.cpp:92] esp_spp_cb(): ESP_SPP_CONG_EVT
Switched to sps of 20
E (59308) BT: port_rfc_closed RFCOMM connection in state 2 closed: Closed (res: 19)
Errorcnt on this session: 0
[I][BluetoothSerial.cpp:71] esp_spp_cb(): ESP_SPP_CLOSE_EVT
E (59317) BT: rfc_find_lcid_mcb LCID reused LCID:0x41 current:0x0
E (59320) BT: RFCOMM_DisconnectInd LCID:0x41

[copercini]

This effect seems gone writing all data with one SerialBT.write() or SerialBT.println call, and not byte by byte
I know, it's not a solution, just a workaround

#include "BluetoothSerial.h"
BluetoothSerial SerialBT;
static uint32_t last_send = 0;
unsigned char testData[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

void setup() {
  SerialBT.begin("ESP32test");
}

void loop() {
  uint32_t now = millis();

  if (SerialBT.hasClient()) {
    if (5000 < now-last_send) {
        SerialBT.write(testData, 26); //buffer, size
      last_send = now;
    }
  }
  delay(1);
}

or with println:

#include "BluetoothSerial.h"
BluetoothSerial SerialBT;
static uint32_t last_send = 0;

void setup() {
  SerialBT.begin("ESP32test");
}

void loop() {
  uint32_t now = millis();

  if (SerialBT.hasClient()) {
    if (5000 < now-last_send) {
        SerialBT.println("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
      last_send = now;
    }
  }
  delay(1);
}

[beegee-tokyo]

@copercini I like workarounds. Will try tomorrow and give feedback.

[beegee-tokyo]

@copercini , tried it and the first one worked for me, together with a reduction of the sending frequency.
Instead of 1 packet every 5ms we send now a bundle of 10 packets every 50ms. That worked at least for a quick test this afternoon.

[beegee-tokyo]

Update:
As I couldn't get my customers project to work as expected, I moved from using Arduino-ESP32 framework to a pure ESP-IDF project using the latest version of ESP-IDF.
Using the bt_spp_acceptor example (which source code is very much the same as BTSerial Arduino code) I got it running without any drop of bytes even at an update rate of 8ms.
So (just guessing, no prove) the problem might be within the ESP-IDF version that Arduino-ESP32 uses (precompiled) and the latest ESP-IDF version. Or within sdkconfig, which I set to give Bluetooth a higher priority than WiFi.
Another test I did was to use BlueKirchens BTstack which gave me even better performance (time to perform a BTSerial write operation) than Espressifs Bluedroid implementation.

Just informing here, no blaming or complaining!

[me-no-dev]

You need to factor in your application design also. If you for example use bt serial in the loop and have other threads running on core 1, it's totally possible that the loop does not get to run often enough. If the code is the same, there should not be any performance difference between Arduino and IDF. Since it's totally fine to compile IDF code inside Arduino, can you try your "pure ESP-IDF" code in Arduino and see what happens? use setup() as app_main()

[beegee-tokyo]

@me-no-dev
You are correct, deeper investigation (like enabling the correct debug log level in ESP-IDF ) showed that the performance of the ESP-IDF BTSerial is as bad as the Arduino-ESP32 BTSerial. Didn't actually expect a difference, because the source codes are basically the same.
Where I hoped to get a difference was that in ESP-IDF I can change the load balance between WiFi and Bluetooth in the menuconfig.

But even selecting to prioritize Bluetooth didn't help.
What is really surprising is that with Bluekitchens BTstack I don't see lost characters or lost packages. They did a really good job.