Hello,
I am trying to get an OV2640 camera working with an ESP32-S3-WROOM N16R8 board (16 MB Flash / 8 MB PSRAM).
I have been troubleshooting this extensively and I have reached a strange situation: the OV2640 works perfectly when I communicate with it manually over SCCB/I2C, but esp_camera_init() fails during SCCB register writes.
I would appreciate any advice on what could cause this.
Hardware / pin configuration
According to the documentation/pinout supplied for the board, I am using:
OV2640 / Camera ESP32-S3 GPIO
--------------------------------
SIOD / SDA GPIO 4
SIOC / SCL GPIO 5
VSYNC GPIO 6
HREF GPIO 7
XCLK GPIO 15
PCLK GPIO 13
Y2 / D0 GPIO 11
Y3 / D1 GPIO 9
Y4 / D2 GPIO 8
Y5 / D3 GPIO 10
Y6 / D4 GPIO 12
Y7 / D5 GPIO 18
Y8 / D6 GPIO 17
Y9 / D7 GPIO 16
PWDN -1
RESET -1
The camera is connected through the board’s FPC camera connector.
Test 1 – SCCB scan without XCLK
Initially I performed an SCCB/I2C scan using:
SDA = GPIO4
SCL = GPIO5
SCCB = 100 kHz
Without XCLK, no device was detected:
Scanning...
NO DEVICES FOUND
Test 2 – SCCB scan with XCLK
I then generated a 20 MHz XCLK on GPIO15 before starting SCCB.
The camera was immediately detected:
XCLK started at 20 MHz
Scanning SCCB bus…
Device found at 0x30
So the OV2640 responds at the expected 7-bit SCCB address 0x30 when XCLK is present.
Test 3 – OV2640 identification
I selected the sensor register bank:
register 0xFF = 0x01
and read the OV2640 identification registers.
I successfully obtained:
PID = 0x26
The sensor can therefore be identified and communicated with.
Test 4 – SCCB read stability
I then performed 100 consecutive PID/VER reads over SCCB at 100 kHz.
Result:
GOOD READS : 100
BAD READS : 0
No SCCB read errors occurred.
Test 5 – SCCB write/read-back stability
I tested repeated register writes using register 0x11, followed by reading the value back.
Result:
GOOD WRITE/READ : 140
BAD WRITE/READ : 0
So normal SCCB writes and reads appear completely stable.
Test 6 – Direct OV2640 initialization sequence
I then manually sent the initial OV2640 register initialization sequence using Wire at 100 kHz, including software reset and the required delay.
Result:
GOOD WRITES : 35
BAD WRITES : 0
PID = 0x26
Every register write succeeded.
This sequence also included registers around the same area where esp_camera had previously failed.
Test 7 – ESP-IDF new I2C master driver
To determine whether Arduino Wire was hiding the problem, I tested the OV2640 directly using the newer ESP-IDF I2C master API:
i2c_new_master_bus()
i2c_master_bus_add_device()
i2c_master_probe()
i2c_master_transmit()
i2c_master_transmit_receive()
Configuration:
Address = 0x30
SCCB/I2C clock = 100 kHz
XCLK = 20 MHz
Result:
Probe 0x30: ESP_OK
PID = 0x26
GOOD READS : 100
BAD READS : 0
GOOD WRITE/READ : 100
BAD WRITE/READ : 0
Therefore the newer ESP-IDF I2C driver can also communicate reliably with this camera.
The problem – esp_camera_init()
When I use the normal ESP32 camera driver:
esp_camera_init(&config);
initialization fails during SCCB writes.
The interesting part is that the failed register changes between attempts.
I have seen:
SCCB_Write Failed addr:0x30, reg:0x23, data:0x00
another time:
SCCB_Write Failed addr:0x30, reg:0x22, data:0x1a
another:
SCCB_Write Failed addr:0x30, reg:0x37, data:0xc3
and with Arduino-ESP32 2.0.17:
SCCB_Write Failed addr:0x30, reg:0x26, data:0x82, ret:-1
camera: Camera probe failed with error 0xffffffff (ESP_FAIL)
Another test failed at:
SCCB_Write Failed addr:0x30, reg:0x61, data:0x70, ret:-1
camera: Camera probe failed with error 0xffffffff (ESP_FAIL)
followed by:
gdma: gdma_disconnect(299): no peripheral is connected to the channel
So it does not consistently fail on one particular OV2640 register.
Arduino versions tested
I originally tested with:
Arduino-ESP32 3.3.11
On that version sccb-ng produced failures such as:
sccb-ng: SCCB_Write Failed ... ret:259
I then downgraded to:
Arduino-ESP32 2.0.17
The problem remains, although the legacy SCCB driver now reports ret:-1.
ESP32-S3 configuration
I am currently using:
Board: ESP32S3 Dev Module
CPU Frequency: 240 MHz
Flash Size: 16 MB
PSRAM: OPI PSRAM
PSRAM is detected successfully:
PSRAM: FOUND
What I have established so far
As far as I can determine:
OV2640 sensor OK
SCCB address 0x30 OK
GPIO4 SDA OK
GPIO5 SCL OK
GPIO15 XCLK OK
SCCB reads 100/100 OK
SCCB write/read 140/140 OK
Manual init writes 35/35 OK
New IDF I2C driver 100/100 reads + 100/100 writes OK
PID 0x26
PSRAM FOUND
esp_camera_init() FAILS
The most confusing part is that manually writing the OV2640 registers works reliably, but the SCCB implementation used inside esp_camera_init() fails at apparently random points in the initialization sequence.
Questions
Does anyone know what could cause esp_camera_init() / the ESP32 camera SCCB driver to fail like this when direct SCCB communication is completely stable?
In particular:
- Is there a known SCCB timing issue with OV2640 + ESP32-S3?
- Does the camera driver send the OV2640 register writes too quickly compared with manual
Wiretransactions? - Should a delay be added between SCCB register writes?
- Is there a known issue with the SCCB implementation in Arduino-ESP32 2.0.17 or 3.3.x?
- Is there a clean way to make
esp_camerause my already-tested SCCB implementation while still using the ESP32-S3 camera DMA/framebuffer driver? - Could XCLK/SCCB timing during
camera_probe()explain why manual communication works butesp_camera_init()does not? - Is there anything board-specific regarding RESET/PWDN or camera power sequencing that could produce this exact behavior?
My immediate goal is simply to get one valid JPEG frame from the OV2640. I am not trying to run a web server yet.
Any suggestions for additional tests or a patch to the SCCB/camera driver would be greatly appreciated.
Thank you.
