MIPI CSI-2 Camera Bring-up

Scope

This application note covers the carrier-board side of bringing up a MIPI CSI-2 camera: configuring the on-module per-camera LDO, routing the CSI lanes, and building the SDK's <alp/camera.h> capture path.

warning

Live capture is unproven on Alp Lab hardware. No camera sensor has been wired on an Alp Lab bench to date, and the reference example is build-verified only (build_only on every platform in its testcase.yaml; its README carries an [UNTESTED]-on-hardware marker). The hardware guidance below — LDO sizing, lane routing, pin assignment — is datasheet-backed and safe to design against. The software walkthrough is a starting point for your own bring-up, not a reproduced result: budget bench time for first light.

Table: Scope summary

Field	Detail
Audience	Firmware engineers integrating a camera sensor into vision workloads.
Prerequisites	QS- guide completed, RPi-compatible MIPI camera module (e.g. RPi V2 or HQ camera).
Outcome	`ai-camera-viewer` builds and flashes against the `<alp/camera.h>` surface. First light on your sensor is your bring-up step.
Time	20 minutes to a flashed image; sensor bring-up is open-ended.
Source	`examples/camera-vision/ai-camera-viewer/` in alp-sdk.

Hardware Setup

The table below is silicon and module hardware, not a software support matrix. See ISP Status for what the SDK actually drives today.

Table: MIPI CSI-2 camera interfaces per family

SoM family	CSI interfaces + LDO
E1M-AEN	1 × 2-lane CSI (`CSI0`). Per-camera LDO: `+V_CAM0` (`Z34`) + `CAM_VFB0` (`Z33`) divider; a second LDO pair `+V_CAM1` (`AB34`) / `CAM_VFB1` (`AB33`) is available as a general-purpose carrier rail.
E1M-X V2N / V2N-M1	2 × 4-lane CSI (`CSI0`, `CSI1`). Per-camera LDOs: `+V_CAM0`…`+V_CAM3` with matching `CAM_VFBx` feedback divider.

Both SoCs carry an on-die ISP block: the Alif Ensemble ISP-Pico (VeriSilicon ISP Nano "Pico") on E4 / E6 / E8 — but not on E3 / E5 / E7 — and an Arm Mali^TM-C55 on the Renesas RZ/V2N. Neither is reachable from the SDK today; ISP Status has the detail.

Place the feedback resistor pair (R1, R2) close to the SoM CAM_VFBx pin; long feedback traces invite oscillation. The output voltage is set by:

V_CAM = 0.6 V × (1 + R₁ / R₂)

ISP Status

No ISP offload is available through the Alp SDK today, on any SoM family. The ISP hardware exists; the software path to it does not. Do not choose an E6 over an E5, or an E1M-X over an E1M-AEN, expecting the SDK to hand you a working ISP.

What that means concretely:

On a default build, alp_camera_configure_isp() returns ALP_ERR_NOSUPPORT. The portable Zephyr video backend that serves the camera class has no in-line ISP surface.
The Alif ISP-Pico backend is registered for E8 only — not E4 or E6 — and cannot currently be enabled: it is opt-in and default-off, it requires the ISP devicetree node (which ships disabled), and it links a vendor HAL wrapper whose shipped version is API-incompatible with the driver. Widening it to E4 / E6 needs explicit backend registrations plus board validation.
Its configure_isp implementation latches the requested configuration into backend state and returns ALP_OK without programming the ISP. The matching parameter upload is pending the Alif ISP-Pico HAL pack.
The Alif vendor-extension surface (3A windows, per-channel gain tables, lens-shading LUTs) returns ALP_ERR_NOSUPPORT from every entry point, for the same reason.

warning

On V2N silicon the SDK compiles a V2N-specific camera backend by default whose configure_isp also latches-and-returns-ALP_OK with no register writes. An ALP_OK from alp_camera_configure_isp() on V2N therefore does not mean the ISP was programmed. Do not gate image quality on that return code.

What is available instead: the sensor pipeline — open / start / stop / capture / release / close — routes through Zephyr's portable video API and is real code, not a stub. Plan on your sensor delivering the pixel format you need directly, and on doing any 3A or tuning work in your application until the HAL pack lands.

Software Walkthrough

west build -b <BOARD> examples/camera-vision/ai-camera-viewer
west flash

The example opens an OV5640 stream at 240 × 240 RGB565 via alp_camera_open(), runs a person-detect model over the frames, and composes the preview plus bounding boxes with LVGL. Two things to know before you build it:

It ships without a model file, to avoid the binary-blob licence question. Compile your own .tflite with Arm's Vela compiler and replace the placeholder buffer in src/inference_loop.c.
Its reference board wiring drives an ST7789 240 × 320 TFT over SPI — not a DSI panel. See AN-004 for the display side.

If alp_camera_open() fails the example does not abort: it logs camera open failed; running with synthetic frame and renders a placeholder preview so the UI layout can be checked against a design mock-up. A running demo is therefore not on its own evidence that your sensor is streaming — confirm the log line is absent.

Troubleshooting

LDO voltage off: divider current too low; reduce R1 + R2 until divider current = 100 × worst-case feedback-pin current (see DS-AEN-001 §7.8 formula).
No CSI link: differential lanes swapped (P/N reversed) or trace impedance not 100 Ω differential.
Lane skew errors: lane-to-lane length mismatch > TBD ps.

References

Example source: examples/camera-vision/ai-camera-viewer/ in alp-sdk; API in include/alp/camera.h. Silicon staging checks: examples/aen/aen-camera-regcheck/, examples/aen/aen-isp-regcheck/ — the ISP check validates the devicetree bind only, with the ISP driver deliberately not enabled, and reports the HAL-wrapper blocker at runtime.
Hardware Design Guides: HG-AEN-001 §5.5, HG-V2N-001 §6.4 (MIPI CSI-2 routing rules).
Datasheet CSI-2 pin tables: §2.3 in each datasheet.

Revision History

Table: Revision History

Revision	Changes	Date
0.1	Initial draft.	May 2026
0.2	Updated SDK references to current layout: example path `examples/camera-vision/ai-camera-viewer/`, added `include/alp/camera.h` and the `aen-camera-regcheck` / `aen-isp-regcheck` reg-checks; corrected the AEN on-die ISP to the Alif Ensemble ISP-Pico (`vsi,isp-pico`); aligned the stream config with the example (240×240 RGB565).	June 2026
0.3	Corrected the ISP story against alp-sdk source: the ISP-Pico backend registers for E8 only (not an E4/E6/E8 support tier), its Kconfig defaults to `n`, and the devicetree node is disabled — so no ISP offload is reachable today and the vendor-ext camera surface returns `ALP_ERR_NOSUPPORT`. Separated the genuine E4/E6/E8 ISP hardware metadata from the support story. Noted that live capture is unproven (no sensor wired on the bench) and that on V2N `configure_isp` returns `ALP_OK` without programming the ISP. Removed a fabricated expected-output log. Fixed the Alp SDK repository links (`alpDevs` → `alplabai`).	July 2026

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Scope​

Hardware Setup​

ISP Status​

Software Walkthrough​

Troubleshooting​

References​

Revision History​