Testing And Validation

E-Ink Display SPI Interface Testing Guide

Board: imx93-jaguar-eink
Target: Hardware validation and signal integrity testing
Audience: Hardware engineers

Overview

This document provides test procedures for validating the E-Ink display SPI interfaces on the imx93-jaguar-eink board. The board provides two SPI options:

QSPI (FlexSPI1) - Preferred, up to 80 MHz, 4-bit data width
Standard SPI (LPSPI1) - Backup, up to 10 MHz, 1-bit data width

Hardware Configuration

Current Working Status ✅❌

❌ FlexSPI1 (QSPI): DISABLED - Not compatible with standard SPI tools (see FlexSPI incompatibility section)
✅ LPSPI1 (Standard SPI): PRIMARY - Should create /dev/spidev1.0 for standard SPI testing

Configuration Change: FlexSPI1 has been disabled in the device tree to avoid conflicts. LPSPI1 is now the primary interface for E-Ink display testing with standard SPI tools.

Expected Result: With this configuration, /dev/spidev1.0 should be available for standard SPI testing tools like spidev_test.

Board Switch Settings

For LPSPI1 (Standard SPI) testing, configure the hardware switches:

Current Configuration - Standard SPI:

Board SPI Mode Switches: 4=X, 3=OFF, 2=ON, 1=ON
Display Mode Switches: BS1=OFF, BS0=ON

Note: QSPI mode is disabled in software but preserved for reference:

QSPI switches would be: 4=X, 3=ON, 2=ON, 1=OFF (BS1=OFF, BS0=OFF)

Signal Connections for Oscilloscope/Logic Analyzer

QSPI Interface (FlexSPI1)

Signal	i.MX93 Pin	Test Point	Expected Voltage
QSPI_CLK	MX93_PAD_SD3_CLK	TP_QSPI_CLK	1.8V → 3.3V
QSPI_CS	MX93_PAD_SD3_CMD	TP_QSPI_CS	1.8V → 3.3V
QSPI_D0	MX93_PAD_SD3_DATA0	TP_QSPI_D0	1.8V → 3.3V
QSPI_D1	MX93_PAD_SD3_DATA1	TP_QSPI_D1	1.8V → 3.3V
QSPI_D2	MX93_PAD_SD3_DATA2	TP_QSPI_D2	1.8V → 3.3V
QSPI_D3	MX93_PAD_SD3_DATA3	TP_QSPI_D3	1.8V → 3.3V

Standard SPI Interface (LPSPI1)

Signal	i.MX93 Pin	Test Point	Expected Voltage
SPI1_CLK	MX93_PAD_SAI1_TXD0	TP_SPI1_CLK	1.8V → 3.3V
SPI1_CS	MX93_PAD_SAI1_TXFS	TP_SPI1_CS	1.8V → 3.3V
SPI1_MOSI	MX93_PAD_SAI1_RXD0	TP_SPI1_MOSI	1.8V → 3.3V
SPI1_MISO	MX93_PAD_SAI1_TXC	TP_SPI1_MISO	1.8V → 3.3V

Control GPIOs

Signal	i.MX93 Pin	Test Point	Expected Voltage
RES_DIS#	MX93_PAD_GPIO_IO08	TP_RESET	1.8V → 3.3V
BUSY	MX93_PAD_GPIO_IO09	TP_BUSY	1.8V → 3.3V
DC	MX93_PAD_GPIO_IO10	TP_DC	1.8V → 3.3V
POWER_EN	MX93_PAD_GPIO_IO11	TP_PWR_EN	1.8V → 3.3V

Software Test Commands

Prerequisites

SSH Setup for Automated Testing

For efficient testing and deployment, configure passwordless SSH access to the target board:

# Copy SSH public key to target board (replace IP as needed)
echo "fio" | ssh-copy-id -f fio@192.168.0.36

# Configure passwordless sudo for fio user
ssh fio@192.168.0.36 "echo 'fio' | sudo -S sh -c 'echo \"fio ALL=(ALL) NOPASSWD: ALL\" > /etc/sudoers.d/fio'"

Benefits:

Enables automated testing scripts without password prompts
Faster iterative development and testing cycles
Required for CI/CD integration and automated deployment

Cross-Compilation Requirements ⚠️

Critical: Development machine (x86_64) and target board (ARM64) use different architectures:

# ❌ WRONG: Local build creates x86_64 binary
cd /local/project/build && make
scp el133uf1_test fio@192.168.0.36:/tmp/  # Fails: "cannot execute binary file"

# ✅ CORRECT: Use Yocto cross-compilation
export KAS_MACHINE=imx93-jaguar-eink
kas-container shell kas/lmp-dynamicdevices-base.yml -c "bitbake eink-spectra6"
scp build/tmp/work/cortexa55-lmp-linux/eink-spectra6/*/image/usr/bin/el133uf1_test fio@192.168.0.36:/tmp/

# Verify architecture before deployment
file el133uf1_test  # Should show "ARM aarch64", not "x86-64"

SPI Interface Verification

SSH into the board and ensure SPI interfaces are available:

# Check available SPI devices
ls -la /dev/spi*

# Expected output:
# /dev/spidev0.0  <- QSPI interface (FlexSPI1) - PRIMARY INTERFACE

Current Status:

✅ FlexSPI1 (QSPI): /dev/spidev0.0 - Working and preferred for E-Ink display
❌ LPSPI1 (Standard SPI): Not available - backup interface, not critical

Note: The device tree uses "spidev" compatible strings for direct hardware testing access. The FlexSPI1 QSPI interface is the primary interface for the E-Ink display and provides higher performance with quad data lines.

Test 1: GPIO Control Signal Testing

Test the display control GPIOs first:

# Test Reset signal (GPIO2_14 = 78)
echo 78 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio78/direction

# Reset pulse - should see LOW then HIGH on oscilloscope
echo 0 > /sys/class/gpio/gpio78/value  # Reset active (LOW)
sleep 0.1
echo 1 > /sys/class/gpio/gpio78/value  # Reset inactive (HIGH)

# Test Data/Command signal (GPIO2_15 = 79)
echo 79 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio79/direction

# Toggle DC signal - should see transitions on oscilloscope
echo 0 > /sys/class/gpio/gpio79/value  # Command mode
sleep 0.1
echo 1 > /sys/class/gpio/gpio79/value  # Data mode

# Test Left/Right Select (GPIO2_16 = 80)
echo 80 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio80/direction

# Toggle L/R selection - should see transitions on oscilloscope
echo 0 > /sys/class/gpio/gpio80/value  # Left panel
sleep 0.1
echo 1 > /sys/class/gpio/gpio80/value  # Right panel

# Test Busy Status (GPIO2_17 = 81) - Input only
echo 81 > /sys/class/gpio/export
echo in > /sys/class/gpio/gpio81/direction
cat /sys/class/gpio/gpio81/value  # Read busy status (0=busy, 1=ready)

# Test Power Enable (GPIO2_11 = 75)
echo 75 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio75/direction

# Power cycle - should see LOW then HIGH on oscilloscope
echo 0 > /sys/class/gpio/gpio75/value  # Power off
sleep 0.5
echo 1 > /sys/class/gpio/gpio75/value  # Power on

# Cleanup
echo 72 > /sys/class/gpio/unexport
echo 74 > /sys/class/gpio/unexport
echo 75 > /sys/class/gpio/unexport

Test 2: QSPI Interface Testing ❌ (Disabled)

Status: FlexSPI1 QSPI interface is DISABLED in device tree for standard SPI testing

Configuration: FlexSPI1 has been disabled to avoid conflicts with standard SPI tools and to focus testing on LPSPI1.

FIXED: SPI device is now properly configured and working on i.MX93 E-Ink board.

Device Tree Configuration Fix

The issue was resolved by fixing the device tree configuration:

Machine Configuration: Added missing KERNEL_MODULE_AUTOLOAD:imx93-jaguar-eink = " spidev"
Device Tree Compatible: Changed from "spidev" to "rohm,dh2228fv" for proper driver binding
Interface Selection: Using LPSPI1 (standard SPI) instead of FlexSPI1 (memory-mapped interface)

Current Working Configuration:

SPI Controller: LPSPI1 at address 44360000.spi (mapped as spi0)
Device Node: /dev/spidev0.0 (automatically created after boot)
Max Speed: 10 MHz (configurable up to higher speeds)
Mode: Standard SPI with CPHA and CPOL support
GPIO Control: Reset, DC, Busy, and LR-select pins properly configured

FlexSPI vs LPSPI:

FlexSPI: Memory-mapped interface for flash devices, uses MTD subsystem (/dev/mtd*)
LPSPI: Standard SPI controller, uses spidev subsystem (/dev/spidev*)

# Install spi-tools if not available
# opkg install spi-tools

# Test SPI with simple data pattern
# This will generate clock and data signals on LPSPI1

# Single byte test - should see 8 clock pulses
echo -n -e '\x55' | spi-pipe -d /dev/spidev0.0 -s 1000000 -b 8

# Pattern test - should see alternating pattern on data lines
echo -n -e '\xAA\x55\xFF\x00' | spi-pipe -d /dev/spidev0.0 -s 5000000 -b 8

# High frequency test - test at maximum speed
echo -n -e '\x01\x02\x04\x08\x10\x20\x40\x80' | spi-pipe -d /dev/spidev0.0 -s 80000000 -b 8

# Continuous pattern for signal integrity testing
for i in {1..100}; do
    echo -n -e '\xAA\x55\xAA\x55' | spi-pipe -d /dev/spidev0.0 -s 10000000 -b 8
    sleep 0.01
done

Test 3: Standard SPI Interface Testing ✅ (Primary)

Status: LPSPI1 is now the primary interface for E-Ink display testing

Expected Device: /dev/spidev1.0 (LPSPI1)

Pre-Test Check:

# Verify spidev device exists
ls -la /dev/spidev1.0
# Expected: /dev/spidev1.0

# Check SPI device in sysfs
ls -la /sys/bus/spi/devices/spi1.0

SPI Communication Tests:

# Test standard SPI with simple data pattern
# This will generate clock, MOSI, and CS signals

# Single byte test - should see 8 clock pulses on SPI1_CLK
echo -n -e '\x55' | spi-pipe -d /dev/spidev1.0 -s 1000000 -b 8

# Pattern test - should see data pattern on MOSI line
echo -n -e '\xAA\x55\xFF\x00' | spi-pipe -d /dev/spidev1.0 -s 5000000 -b 8

# Maximum frequency test for standard SPI
echo -n -e '\x01\x02\x04\x08\x10\x20\x40\x80' | spi-pipe -d /dev/spidev1.0 -s 10000000 -b 8

# Continuous pattern for signal integrity testing
for i in {1..100}; do
    echo -n -e '\xF0\x0F\xF0\x0F' | spi-pipe -d /dev/spidev1.0 -s 8000000 -b 8
    sleep 0.01
done

Test 4: Frequency Sweep Testing

Test different frequencies to verify signal integrity:

# QSPI frequency sweep
echo "Testing QSPI at different frequencies..."
for freq in 1000000 5000000 10000000 20000000 40000000 80000000; do
    echo "Testing QSPI at ${freq} Hz"
    echo -n -e '\xAA\x55\xAA\x55' | spi-pipe -d /dev/spidev0.0 -s $freq -b 8
    sleep 0.5
done

# Standard SPI frequency sweep  
echo "Testing Standard SPI at different frequencies..."
for freq in 1000000 2000000 5000000 8000000 10000000; do
    echo "Testing SPI at ${freq} Hz"
    echo -n -e '\xAA\x55\xAA\x55' | spi-pipe -d /dev/spidev1.0 -s $freq -b 8
    sleep 0.5
done

Test 5: Level Shifter Direction Testing

Test autosensing vs fixed direction level shifters:

# This test attempts to read from the SPI device
# Autosensing buffers should handle bidirectional signals
# Fixed direction buffers will only work for write operations

# Test read operation (requires autosensing buffers)
echo "Testing SPI read operation (requires autosensing level shifters)..."

# Send command and try to read response
# This will fail with fixed direction buffers
spi-pipe -d /dev/spidev0.0 -s 1000000 -b 8 -r 4 <<< $'\x9F\x00\x00\x00'

# If the above command returns data, autosensing buffers are working
# If it times out or returns zeros, you may have fixed direction buffers

Expected Signal Characteristics

Timing Requirements

QSPI Interface:

Clock Frequency: 1 MHz to 80 MHz
Setup Time: > 2 ns
Hold Time: > 2 ns
CS Setup: > 5 ns before first clock edge
CS Hold: > 5 ns after last clock edge

Standard SPI Interface:

Clock Frequency: 1 MHz to 10 MHz
Setup Time: > 5 ns
Hold Time: > 5 ns
CS Setup: > 10 ns before first clock edge
CS Hold: > 10 ns after last clock edge

Signal Integrity Checks

Voltage Levels:

i.MX93 Side: 1.8V ±10% (1.62V - 1.98V)
Display Side: 3.3V ±10% (2.97V - 3.63V)
Logic High: > 70% of VDD
Logic Low: < 30% of VDD

Signal Quality:

Rise/Fall Time: < 10% of clock period
Overshoot: < 20% of VDD
Undershoot: < 20% of VDD
Jitter: < 5% of clock period

Troubleshooting

SPI Device Not Found (FIXED)

Issue: /dev/spidev0.0 doesn't exist after boot

Root Cause: Missing kernel module autoload and incorrect device tree compatible string

Solution Applied:

Machine Configuration Fix (imx93-jaguar-eink.conf):

KERNEL_MODULE_AUTOLOAD:imx93-jaguar-eink = " spidev"

Device Tree Fix (imx93-jaguar-eink.dts):

eink_display_spi: eink@0 {
    compatible = "rohm,dh2228fv";  // Changed from "spidev"
    reg = <0>;
    spi-max-frequency = <10000000>;
    // ... rest of configuration
};

Manual Workaround (if needed on older builds):

# Set driver override
echo spidev | sudo tee /sys/bus/spi/devices/spi0.0/driver_override

# Bind the driver
echo spi0.0 | sudo tee /sys/bus/spi/drivers/spidev/bind

# Fix permissions
sudo chmod 666 /dev/spidev0.0

Common Issues

No SPI Activity:

Check hardware switch settings
Verify power supply (3.3V and 1.8V rails)
Check device tree configuration
Verify GPIO control signals

Signal Integrity Issues:

Check level shifter power supplies
Verify ground connections
Check for proper termination
Measure signal integrity at both sides of level shifters

Level Shifter Direction Issues:

Autosensing buffers may need pull-up/pull-down resistors
Check if attached devices affect direction sensing
Consider switching to fixed direction buffers for write-only operation

Debug Commands

# Check SPI driver status
cat /proc/interrupts | grep spi

# Check device tree configuration
cat /proc/device-tree/soc@0/bus@42000000/spi@42360000/status
cat /proc/device-tree/soc@0/bus@42000000/flexspi@425e0000/status

# Check GPIO status
cat /sys/kernel/debug/gpio

# Monitor kernel messages
dmesg | grep -i spi

Test Report Template

Document your test results using this template:

SPI Interface Test Report
========================
Date: ___________
Tester: ___________
Board Serial: ___________

Hardware Configuration:
- Board SPI Mode Switches: ___________
- Display Mode Switches: ___________
- Level Shifter Type: ___________

QSPI Interface Tests:
- GPIO Control Signals: PASS/FAIL
- 1 MHz Operation: PASS/FAIL  
- 10 MHz Operation: PASS/FAIL
- 80 MHz Operation: PASS/FAIL
- Signal Integrity: PASS/FAIL
- Voltage Levels: _____ V (i.MX93), _____ V (Display)

Standard SPI Interface Tests:
- GPIO Control Signals: PASS/FAIL
- 1 MHz Operation: PASS/FAIL
- 10 MHz Operation: PASS/FAIL  
- Signal Integrity: PASS/FAIL
- Voltage Levels: _____ V (i.MX93), _____ V (Display)

Level Shifter Tests:
- Direction Sensing: PASS/FAIL
- Bidirectional Operation: PASS/FAIL

Issues Found:
___________

Recommendations:
___________

Safety Notes

ESD Protection: Use proper ESD protection when probing signals
Probe Loading: Use high-impedance probes (>1MΩ) to avoid signal loading
Power Sequencing: Ensure proper power-up sequence (1.8V before 3.3V)
Hot Plugging: Do not connect/disconnect probes while system is powered

For questions or issues, contact the software team with test results and oscilloscope captures.

Testing And Validation

E-Ink Display SPI Interface Testing Guide

Overview

Hardware Configuration

Current Working Status ✅❌

Board Switch Settings

Signal Connections for Oscilloscope/Logic Analyzer

QSPI Interface (FlexSPI1)

Standard SPI Interface (LPSPI1)

Control GPIOs

Software Test Commands

Prerequisites

SSH Setup for Automated Testing

Cross-Compilation Requirements ⚠️

SPI Interface Verification

Test 1: GPIO Control Signal Testing

Test 2: QSPI Interface Testing ❌ (Disabled)

Device Tree Configuration Fix

Test 3: Standard SPI Interface Testing ✅ (Primary)

Test 4: Frequency Sweep Testing

Test 5: Level Shifter Direction Testing

Expected Signal Characteristics

Timing Requirements

Signal Integrity Checks

Troubleshooting

SPI Device Not Found (FIXED)

Common Issues

Debug Commands

Test Report Template

Safety Notes

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