RTL8735BDM (AmebaPro2) — MIPI CSI-2 lane configuration query for IMX327 sensor support

Linux Multimedia
1

Hi,

We’re using the RTL8735BDM (AmebaPro2) in our video doorbell product, building against the ameba-rtos-pro2 SDK release (9.6_r): GitHub - Ameba-AIoT/ameba-rtos-pro2: Realtek Official IoT Software Development Kit for Ameba Series SoC: (Ameba Pro2) · GitHub

We’re evaluating adding a Sony IMX327 sensor via a camera module that connects over a 15-pin FPC, which physically wires only 2 MIPI CSI-2 data lanes (lane0 + lane1, plus clock) to the RTL8735BDM — lanes 2 and 3 are not routed on our board. The SDK’s sensor.h already defines SENSOR_IMX327, with sensor_imx327.bin and iq_imx327.bin present under component/soc/8735b/fwlib/rtl8735b/lib/source/ram/video/voe_bin/.

We couldn’t find any lane-count configuration exposed in the SDK source (module_video.c, video_user_boot.c, sensor.h) — it appears to be baked into these binary blobs. Could you help confirm:

  1. Is sensor_imx327.bin / iq_imx327.bin configured for 2-lane or 4-lane MIPI CSI-2 receive on the ISP side?
  2. If it’s currently tuned for 4-lane, is a 2-lane-configured variant of this blob available, or can it be retuned/rebuilt for 2-lane operation?
  3. More generally — is there a supported way to select/override MIPI lane count per sensor from application code, rather than it being fixed inside the blob?
  4. Separately, just to sanity-check our own board design assumption: does a 15-pin camera FPC connector (the common Raspberry-Pi-style camera connector convention) support 4-lane MIPI CSI-2 at all, or is that pin count inherently limited to 2 lanes plus clock? We’ve assumed the latter (not enough conductors for 4 data lanes + clock + grounds in 15 pins) but wanted to confirm against your experience with other customer designs.
2

Hi @deepakkumarbinwal

You are absolutely right that it is compiled into a binary file. The source codes can be found here in the repository. The link should direct you to our drivers for IMX327.

  1. Our default sensor_imx327.bin is meant for a 2-lane configuration, but you can always recompile it to a 4-lane MIPI setup in static int imx327_get_init_info() from the sensor_imx327_mipi.c. The IQ is not affected by the lane configurations.
  3. I have not experimented with changing the MIPI lane count from the application code, do let me know if you wish to do so. I will try to see if it is doable.
  4. Unfortunately (or fortunately), the 15-pin configuration that is compatible with the RaspberryPi only has 2 MIPI lanes on them so that means our sensor_imx327.bin should work right out the box. I had successfully tested the drivers with a 15-pin IMX327 from Arducam on the AMB82-Mini months back so you should be fine.
    Furthermore, only the 22-pin variants can potentially support up to 4 lanes. You may refer to this documentation to see the pinout for 15/22-pins.