ESP32 Forum

Hardware: ESP32-WROOM-32E Module 4MB (ESP32-D0WD-V3 (revision 3))
Software: Arduino IDE with ESP32 Board V1.0.6

Configuration:
Selected Board: ESP32 Dev Module (esp32)
PSRAM: Disable
Partition Scheme: Minimal SPIFFS(1.9MB APP With OTA/190KB SPIFFS)
CPU Frequency: 240 MHz
Flash Mode: QIO
Flash Frequency: 80MHz
Flash Size: 4MB(32Mb)
Upload Speed:921600

Issue:

I have a 321 byte of file in SPIFFS, I read it in a 10KB char array type buffer. and Print it on Serial Port and TCP/IP Port, 4 times Without any operation on this Buffer.
Case 1: USB TTL Connected
All 4 times Buffer Printed Perfectly on both Serial Port and TCP/IP Port.

Case 2: USB TTL Not Connected
Data on TCP/IP:
1st time buffer Prints Perfectly.
2nd Time buffer print garbage data print.
3rd Time mostly garbage data print,
4th time most time garbage data print.

Issue is not generated in smaller size sample code. So can't share sample Code.

My Code build Analysis:
Sketch uses 1230490 bytes (62%) of program storage space. Maximum is 1966080 bytes.
Global variables use 90032 bytes (27%) of dynamic memory, leaving 237648 bytes for local variables. Maximum is 327680 bytes.

I tried to connect USB TTL pin one by one, first Connect TX Pin(ESP32) Only, Issue is generated. but when connect only TX Pin there is not issue. After that I have pulled up RX Pin with 4.7K. then my issue is solved permanently.

So, I want to know why this behavior occurs? What are causes this type of issue. and what's it Solution.

That doesn't really make sense from a hardware point of view... is RX the only thing you disconnect? Can we see your code?

Hello,

I disconnect both TX and RX pin of USB TTL and ESP32. But I test my issue in below cases :
1) Connect Only TX Pin(ESP32) to USB TTL RX - Have Issue
2) Connect Only RX Pin(ESP32) to USB TTL TX - No Issue
3) TX and RX both Connected to USB TTL - No Issue
4) Disconnect RX and TX both and pullup RX Pin(ESP32) - No Issue

So looking to know is there any reason for this type of behaviour.

Thank You