UART Communication Delays and Data Loss

[mightChamp]

Board

ESP32 Wroom 32E 4MB Flash

Device Description

We are making an Uart Data logger, an external device send uart data, which stored in SD card.

Hardware Configuration

GPIO13- Uart TX, and GPIO14- Uart RX
Uart setup:
Baud Rate: 115200
Flow Control: Disabled
Buffer Size: 4096

Version

latest development Release Candidate (RC-X)

IDE Name

Arduino IDE

Operating System

Windows 11

Flash frequency

80Mhz

PSRAM enabled

no

Upload speed

921600

Description

We are encountering an issue with UART communication on ESP32 where data reception is delayed, and sometimes data is lost. This issue occurs intermittently and was not present in version v1.0.6.

Sketch

void setup() {
    Serial.begin(115200);  // UART initialized at 115200 baud rate
}

void loop() {
    if (Serial.available()) {
        String data = Serial.readString();
        Serial.println(data);
    }
}

Debug Message

No Debug Message

Other Steps to Reproduce

Set up UART communication between ESP32 and another device.
Send continuous data streams over UART.
Observe occasional delays and missed data.

I have checked existing issues, online documentation and the Troubleshooting Guide

• I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[lbernstone]

The HardwareSerial library has been modified to have more capabilities for handling intermittent and burst data flows. Take a look at the OnReceive and RxTimeout examples to see how to handle high activity and sporadic flows.
@SuGlider This could definitely use some doco

[SuGlider]

@mightChamp - The issue is related only to Core 3.1.0-RC1? Does it also happen with Core 3.0.5?

[SuGlider]

This sounds related to #10397
After testing the sketch from the issue, it seems clear that IDF 4.x and 5.x UART Driver used by ESP32 Arduino HardwareSerial is not efficient and causes a huge performance issue.

The evidence is that whenever Serial0.begin() is executed, there is a significative time slot reduction to the main Arduino Task, affecting the time that loop() has to process data.

In Arduino Core 1.0.6, the UART driver was local one, faster and way more efficient.
The solution for this issue is to refactor HardwareSerial and create its own Arduino UART Driver, the same way it is done for SPI.
@me-no-dev - FYI.

[SuGlider]

@mightChamp - Could you please check if PR #10428 solves this issue too?
This PR improves the loop() execution efficiency and may give it more "CPU cycles" in order to solve the data loss issue.