ESP32-PICO-V3 won't go in download mode

[jacopo99]

Hi all,

I've designed a very simple board using the esp32-pico-v3 and an external flasher using a CP2102.
when I try to flash anything, I get this error:

Code: Select all

esptool.py v3.3
Serial port COM6
Connecting.....................................An error occurred while uploading the sketch
.

A fatal error occurred: Failed to connect to ESP32: No serial data received.
For troubleshooting steps visit: https://docs.espressif.com/projects/esptool/en/latest/troubleshooting.html

Arduino IDE 1.8.16, Windows 11, driver version 11.1.0.53, board selected esp32 pico-d4 115200

You can find the schematics attached. I added external 100nF caps on GPIO0 and EN to GND, and an add 10uF cap on EN. The result is still the same if I reset manually the circuit using 2 buttons.
I bought a cp2102 adapter and I still have the same problem.

1.png (128.37 KiB) Viewed 5182 times

2.png (172.78 KiB) Viewed 5182 times

Thanks in advance

[ESP_Sprite]

You swapped U0TXD and U0RXD twice, meaning the Rx of your serial-USB chip is connected to the Rx of the ESP32.

[boarchuz]

Are you missing a pullup on EN?
Also you need separate 5.1k resistors for each USB CC pin. Raspberry Pi had well-publicised problems sharing the resistor like that.

[jacopo99]

You swapped U0TXD and U0RXD twice, meaning the Rx of your serial-USB chip is connected to the Rx of the ESP32.

Hi, thanks for the reply.
Are you sure about it? They seem ok to me.
I swapped them in the SCH so that I don't have to remember it every time. (I anyway tried to swap them IRL just to double check)

[ESP_Sprite]

Hi, thanks for the reply.
Are you sure about it? They seem ok to me.
I swapped them in the SCH so that I don't have to remember it every time. (I anyway tried to swap them IRL just to double check)

Yes. U0RXD of the ESP32 goes to pin 2 of the header. On the other side, pin 2 of the header is called U0TXD (swap 1), but then that line runs to U0RXD of the CP2102 (swap 2)

[jacopo99]

Hi, thanks for the reply.
Are you sure about it? They seem ok to me.
I swapped them in the SCH so that I don't have to remember it every time. (I anyway tried to swap them IRL just to double check)

Yes. U0RXD of the ESP32 goes to pin 2 of the header. On the other side, pin 2 of the header is called U0TXD (swap 1), but then that line runs to U0RXD of the CP2102 (swap 2)

thanks for that.
Just tried again and still, nothing, got the same error.

[jacopo99]

Are you missing a pullup on EN?
Also you need separate 5.1k resistors for each USB CC pin. Raspberry Pi had well-publicised problems sharing the resistor like that.

Hi, thanks for pointing that out.
Yes, I already changed it for the next rev of the PCB. I checked the voltages on the uart bridge and both vbus and 3.3v are ok, so I should be ok. I managed to write to the CP2102 EEPROM using their Silabs utility, so the link should be fine.

Externally I a pull-up both from gpio0 and EN to 3v3. Then I tried without one on GPI0 but still nothing, And then I tried without any, but still nothing. Multimeter shows that voltage drops to 0 and goes back to 3v3 correctly using the push-buttons.

[jacopo99]

Ok,

I revisioned the schematic and added all the necessary fixes. There's also the EN 10uF cap and pullup res onboard now.

I'll route the PCB and see if it works this time around, but the error was anyway quite odd. II suspect it might be on the esp32 side.

Schematic v2.png (170.72 KiB) Viewed 4993 times

[jacopo99]

Yes. U0RXD of the ESP32 goes to pin 2 of the header. On the other side, pin 2 of the header is called U0TXD (swap 1), but then that line runs to U0RXD of the CP2102 (swap 2)

Hi there,
I assembled the new version of the board and switched to ESP-Prog as a programmer, to take out a variable that might be going wrong.
I tried both via UART and via JTAG. UART is completely empty, JTAG throws this:

Code: Select all

CURRENT: upload_protocol = esp-prog
Uploading .pio\build\pico32\firmware.bin
Open On-Chip Debugger  v0.11.0-esp32-20220706 (2022-07-06-15:48)
Licensed under GNU GPL v2
For bug reports, read
        http://openocd.org/doc/doxygen/bugs.html
debug_level: 1

adapter speed: 20000 kHz

WARNING: boards/esp-wroom-32.cfg is deprecated, and may be removed in a future release.
adapter speed: 5000 kHz

Error: JTAG scan chain interrogation failed: all zeroes
Error: Check JTAG interface, timings, target power, etc.
Error: Trying to use configured scan chain anyway...
Error: esp32.cpu0: IR capture error; saw 0x00 not 0x01
Warn : Bypassing JTAG setup events due to errors
Error: Unexpected OCD_ID = 00000000
Warn : target esp32.cpu0 examination failed
Error: Unexpected OCD_ID = 00000000
Warn : target esp32.cpu1 examination failed
Error: JTAG scan chain interrogation failed: all zeroes
Error: Check JTAG interface, timings, target power, etc.
Error: Trying to use configured scan chain anyway...
Error: esp32.cpu0: IR capture error; saw 0x00 not 0x01
Warn : Bypassing JTAG setup events due to errors
Error: Unexpected OCD_ID = 00000000
Error: Unexpected OCD_ID = 00000000
Error: Target not examined yet
Error: Target not examined yet
Error: Unexpected OCD_ID = 00000000
embedded:startup.tcl:1184: Error: ** Unable to reset target **
in procedure 'program_esp'
in procedure 'program_error' called at file "C:/Users/jacop/.platformio/packages/tool-openocd-esp32/share/openocd/scripts/target/esp_common.cfg", line 104
at file "embedded:startup.tcl", line 1184
*** [upload] Error 1

[ESP_Sprite]

Looks like your ESP32 is not booted up. What's the level on EN? 3.3V still stable?

EDIT: Perhaps I'm missing it, but is EN pulled up anywhere now? I still don't see it in the schematic.