ESP32E prototype PCB always enters download mode on cold boot

[HighVoltage]

I have designed a prototype PCB with ESP-WROOM-32E module. I have followed the reference schematic at below link for powering and button control. I don't use USB interface, just serial header for programming, and minor other additions: level shifter, serial conversion IC.

https://dl.espressif.com/dl/schematics/ ... v4-sch.pdf

I have an issue that cold boot always wants to enter download mode. If I use EN button to reset, application starts normally. I have continuity tested the PCB, there is no errant grounding of IO0. I have read the strapping pins documentation carefully and can't understand why I am getting this behavior. IO0 should be pulled high internally. My button is working as expected, only making ground when depressed.

The boot message seem curious, and not always consistent. Mostly boot value is 0x3, on button reset, switches to 0x13. Also occasionally get a "NO_MEAN". Here are some trial cold boots, almost always goes to download mode on cold boot, but always goes to run app on reset with button. Appreciate any advice to debug.

Code: Select all

rst:0x1 (POWERON_RESET),boot:0x3 (DOWNLOAD_BOOT(UART0/UART1/SDIO_REI_REO_V2))
waiting for download
ets Jul 29 2019 12:21:46

rst:0x0 (NO_MEAN),boot:0x0 (DOWNLOAD_BOOT(UART0/UART1/SDIO_FEI_FEO_V2))
ets_main.c 404 
ets Jul 29 2019 12:21:46

rst:0x1 (POWERON_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:1
load:0x3fff0030,len:9004

[ESP_Sprite]

Remove your equivalent of C15. It's still in the schematic for some reason, but on actual boards, we don't place it anymore.

[HighVoltage]

That did it! Works perfectly now, thanks!