710 E-Beam Inspection Pixel Core :: Quicker, easier and cheaper to make your own chip!

E-Beam Inspection Pixel Core

An 8-bit pixel processing core designed for electron beam inspection systems. This module processes pixel data in real-time, performing defect detection through multiple algorithms including running mean calculation, local contrast analysis, and edge detection.

How it works

The core accepts 8-bit pixel values on the ui_in inputs, synchronized with a pix_valid signal on uio_in[0]. It maintains a running mean using an Infinite Impulse Response (IIR) filter to track local brightness levels.

Key features:

Running Mean (IIR): Continuously updates the average pixel value using a configurable alpha factor
Local Contrast: Computes |pixel - mean| to detect brightness variations
Edge Detection: Calculates |pixel - previous_pixel| to identify edges
Configurable Thresholds: SPI interface allows runtime adjustment of detection parameters
Defect Flags: Outputs binary flags for edge, dark defect, bright defect, and any defect conditions
Magnitude Output: Provides a 4-bit magnitude nibble representing the strength of detected features

SPI Configuration Interface

CSn: Chip select (active low) on uio_in[2]
SCLK: Serial clock on uio_in[3]
MOSI: Master out slave in on uio_in[4]
MISO: Master in slave out on uio_out[5]

Configurable registers:

Threshold values for contrast and edge detection
IIR filter alpha shift parameter
Mode selection register

Output Format

The uo_out provides:

uo_out[7]: defect_any - Any defect condition detected
uo_out[6]: bright_defect - Pixel significantly brighter than local mean
uo_out[5]: dark_defect - Pixel significantly darker than local mean
uo_out[4]: edge_strong - Strong edge detected
uo_out[3:0]: mag_nib - 4-bit magnitude of the strongest detected feature

How to test

Apply pixel data to ui_in[7:0]
Assert pix_valid on uio_in[0] when pixel data is valid
Use frame_start on uio_in[1] to reset frame-based processing if needed
Configure detection thresholds via SPI interface
Monitor defect flags and magnitude on uo_out[7:0]

SPI Register Access

Write operations: Send 8-bit address followed by 8-bit data
Read operations: Send 8-bit address, then read 8-bit data on MISO

External hardware

This is a digital processing core designed for integration into larger inspection systems. No external hardware required for basic operation.

IO

#	Input	Output	Bidirectional
0	pixel[0]	mag[0]	pix_valid
1	pixel[1]	mag[1]	frame_start
2	pixel[2]	mag[2]	spi_cs_n
3	pixel[3]	mag[3]	spi_sclk
4	pixel[4]	edge_strong	spi_mosi
5	pixel[5]	dark_defect	spi_miso
6	pixel[6]	bright_defect
7	pixel[7]	defect_any

710 E-Beam Inspection Pixel Core