ESP32‑P4 + ESP32‑C5（WT01P4C5‑S1）WiFi init fails with RuntimeError: Wifi Unknown Error 0xffffffff

[hatsuneIridium]

Hi everyone,
I’m using the Wireless‑Tag WT01P4C5‑S1 board, which has ESP32‑P4 (host) and ESP32‑C5 (WiFi/BLE co‑processor) on board, connected via SDIO.
Board info: https://www.wireless-tag.com/product-item-101.html
You can download the document for the Wireless-Tag WT01P4C5-S1 board from the board info.

My setup

P4 firmware:
Official MicroPython GENERIC_ESP32P4 with Support for external C5 WiFi/BLE (v1.28.0, 2026‑04‑06).
Repo:https://micropython.org/download/ESP32_GENERIC_P4/
C5 firmware:
Built from espressif/esp‑hosted‑mcu (latest main branch, no code changes) for ESP32‑C5, flashed as the slave co‑processor firmware.
Repo: https://github.com/espressif/esp-hosted-mcu
Transport: SDIO (on‑board wiring as per manufacturer schematic).
ESP‑IDF version for building C5 fw: 5.5.4(as required by esp‑hosted‑mcu).

Minimal test code (REPL)

import network
wlan = network.WLAN(network.STA_IF)
wlan.active(True)  # <-- crashes here

Error

MPY: soft reboot
Traceback (most recent call last):
  File "<stdin>", line 3, in <module>
RuntimeError: Wifi Unknown Error 0xffffffff

The error happens immediately at wlan.active(True), before any connect or scan.
What I’ve checked
Both chips flash successfully; basic GPIOs/UART work.
C5 runs the esp‑hosted‑mcu slave firmware (no obvious boot errors on serial).
P4 MicroPython is the correct “external C5” variant.
This is not a “flash C5 with MicroPython” mistake — C5 is running the Espressif co‑processor firmware.

My question / ask for help

Are there any specific sdkconfig / menuconfig options I must set when building esp‑hosted‑mcu for ESP32‑C5 as SDIO slave to work with MicroPython’s external WiFi driver?
Does MicroPython’s network module for “external C5” require a specific version or branch of esp‑hosted‑mcu?
Are there known issues with ESP32‑P4 + C5 over SDIO in current MicroPython / esp‑hosted‑mcu?
I also opened an issue yesterday with the same problem:#19217
Any guidance on correct C5 firmware build config, required pins, or debug steps would be greatly appreciated.
Thanks!

[WangilaWakhongola]

This is a known issue with the ESP32-P4 + ESP32-C5 combo module. The WiFi runs on the C5 co-processor, which requires the correct firmware on both chips.
Try this:
pythonimport network
import time

wlan = network.WLAN(network.STA_IF)
wlan.active(False)
time.sleep(1)
wlan.active(True) # Give the C5 time to initialize
time.sleep(2)

wlan.connect('SSID', 'PASSWORD')
Also check:

You're using MicroPython firmware specifically built for ESP32-P4 with C5 co-processor support
The C5 firmware is up to date — flash it separately via esptool if needed
Try wlan.active(False) before True to force a clean reset of the WiFi co-processor

If the error persists, it's likely a firmware incompatibility — report it on the MicroPython GitHub with your firmware version.

[projectgus]

This is a known issue with the ESP32-P4 + ESP32-C5 combo module

wlan.active(True) # Give the C5 time to initialize

@WangilaWakhongola Do you have a reference for this? If there are boards that need the time.sleep(1) and time.sleep(2) to initialise then this is a bug we should fix in MicroPython.

[WangilaWakhongola]

I don't have a reference for that, so I may be mistaken. I was basing the comment on anecdotal examples where adding a short time.sleep() appeared to fix startup timing issues on some boards. If this is genuinely required for certain hardware, I agree it should be treated as a MicroPython bug rather than a recommended workaround. If anyone has a reproducible example or an existing issue, I'd appreciate the link.

[Tangerino]

Please take a look here. It might help https://github.com/Tangerino/micropython-p4-test-suite Carlos

…

On Mon, Jun 29, 2026 at 4:58 PM W .WAKHONGOLA ***@***.***> wrote: This is a known issue with the ESP32-P4 + ESP32-C5 combo module. The WiFi runs on the C5 co-processor, which requires the correct firmware on both chips. Try this: pythonimport network import time wlan = network.WLAN(network.STA_IF) wlan.active(False) time.sleep(1) wlan.active(True) # Give the C5 time to initialize time.sleep(2) wlan.connect('SSID', 'PASSWORD') Also check: You're using MicroPython firmware specifically built for ESP32-P4 with C5 co-processor support The C5 firmware is up to date — flash it separately via esptool if needed Try wlan.active(False) before True to force a clean reset of the WiFi co-processor If the error persists, it's likely a firmware incompatibility — report it on the MicroPython GitHub with your firmware version. — Reply to this email directly, view it on GitHub <#19221?email_source=notifications&email_token=AAYEPRCVEKPAFMJNBWPVXJL5CJ723A5CNFSNUABIM5UWIORPF5TWS5BNNB2WEL2ENFZWG5LTONUW63SDN5WW2ZLOOQXTCNZUG4ZDSOBQUZZGKYLTN5XKU43VMJZWG4TJMJSWJJLFOZSW45FMMZXW65DFOJPWG3DJMNVQ#discussioncomment-17472980>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAYEPREJU5UKIHZ6H4LAGZL5CJ723AVCNFSNUABHKJSXA33TNF2G64TZHMYTKMZTG4YTIMR3IRUXGY3VONZWS33OHMYTAMBWGQ2TOMVBOYBA> . You are receiving this because you are subscribed to this thread.Message ID: <micropython/micropython/repo-discussions/19221/comments/17472980@ github.com>

-- *Merci beaucoup, Muito obrigado, Thanks* *Carlos TangerinoMobile: +33 6 82 05 55 18*

[easytarget]

RuntimeError: Wifi Unknown Error 0xffffffff

This error typically means the main CPU cannot talk to the co-processor at all. It sounds like you have correct versions for the main and hosted cpus

EDITED!

I looked at the datasheet linked from that (Chinese) document. It lists the P4<->C5 pin mapping:

This is different from the default pin mapping given here:
https://github.com/espressif/esp-hosted-mcu/blob/main/docs/sdio.md#esp32-p4-function-ev-board-host-pin-mapping

Specifically: It looks like they use a different pin mapping on the P4; (using default C6 pins rather than the default C5 ones!)

If you are building the C5 firmware yourself you will need to follow the steps in https://github.com/espressif/esp-hosted-mcu/blob/main/docs/sdio.md to make sure it uses SDIO transport. The physical pin mapping on the C5 itself looks correct, so you do not need to change pins when building the C5 firmware.

And you need to ensure that the fP4 irmwares has the correct pins configured for the SDIO bus, I do this in .../BOARD/sdkconfig.board for my ESP32-P4/C6 based Tab5 board:

• If you have already done this, my apologies, but you don't mention it so I am guessing that the issue here is with specifying the pins used for the SDIO bus.

In the working config I created for my Tab5 firmware I have:

# Enable WiFi
#  taken from M5Stack port config for the TAB-5 board.
CONFIG_ESP_HOSTED_P4_DEV_BOARD_NONE=y
CONFIG_ESP_HOSTED_PRIV_SDIO_PIN_CMD_SLOT_1=13
CONFIG_ESP_HOSTED_PRIV_SDIO_PIN_CLK_SLOT_1=12
CONFIG_ESP_HOSTED_PRIV_SDIO_PIN_D0_SLOT_1=11
CONFIG_ESP_HOSTED_PRIV_SDIO_PIN_D1_4BIT_BUS_SLOT_1=10
CONFIG_ESP_HOSTED_PRIV_SDIO_PIN_D2_4BIT_BUS_SLOT_1=9
CONFIG_ESP_HOSTED_PRIV_SDIO_PIN_D3_4BIT_BUS_SLOT_1=8
CONFIG_ESP_HOSTED_SDIO_GPIO_RESET_SLAVE=15

This works and connects using the esp-32 C6 as the co-processor. The specific pins may be different on your board but the principle is the same.

finally: My tab5's C6 co-processor has (factory flashed) esp-hosted based on IDF 5.4.x. I can talk to it with my IDF 5.5.4 based P4 port and connect, so some cross-matching of versions is possible.

[projectgus]

Thanks for sharing these details, @easytarget.

For what it's worth, if anyone has config like this for a particular board then we'd welcome a PR to add a new board definition to MicroPython. Please let me know if you could use more pointers about how to do this.

[easytarget]

Thanks @projectgus ; when I have something worthwhile to share I will. ;-)

I have my work-in-progress board definition + build instructions here:
https://codeberg.org/easytarget/m5-tab5-micropython/src/branch/main/firmware

But at present I only have wifi working and a couple of other bits (extended gpio + power management, RTC and IMU); It needs to at least have LVGL working before it's worth sharing widely. Ideally the camera and I2S audio dac & adc's too.

It's also a relatively low-priority, off/on project; M5Stack have a working UIFlow micropython port (afik based on mpy v1.26) but it has very convoluted config, blobs of C-Code added here and there, and does not fill me with joy. But at least gives me hope that it can be made to work.

[projectgus]

Nice progress! Looks like you've got quite a lot working.

For what it's worth I think even a basic Tab5 board definition that sets the SDIO pins and maybe defines the pins for the other internal peripherals would be worth upstreaming as a first step, if you were up for that. People can always install Python drivers for other peripherals (at least, the ones which are pure Python), or make their own custom build based on the upstream definition.