RT214 Integration Guide

Introduction

The RT214 is an area image engine designed for barcode reading. It features an integrated illumination LED and an aiming LED.

LED Compliance Statement: The RT214 complies with IEC 62471:2006 for LED safety.

The RT214 comprises:

A CMOS image sensor and its lens
An LED-based illumination system
An LED aiming system

System Block Diagram (Figure 1-1): The system consists of a Mainboard containing a CMOS sensor, Aiming LED, Decoding Chip, and Connector. The CMOS sensor interfaces with the Decoding Chip, which also receives input from the Aiming LED and Illumination LED. The Decoding Chip is connected to the main Connector.

Illumination

The RT214 is equipped with a white LED that provides supplementary lighting, enabling barcode scanning even in complete darkness. The illumination can be controlled via software to be turned On or Off.

Aimer

A red LED aimer is included to assist users in easily positioning the target barcode within the engine's field of view, thereby enhancing scan efficiency. The aiming pattern can be toggled On or Off. It is recommended to keep the aimer active during standard barcode scanning. For scenarios involving diverse backgrounds, varying colors, or strong ambient light/backlight conditions, it is advisable to disable the aimer.

General Requirements

This section details the installation process for the RT214, including general requirements, housing design considerations, and physical and optical information.

⚠️ Caution: Avoid touching the imaging lens during installation to prevent fingerprints. ⚠️ Caution: Do not touch the illumination LED during handling, as improper handling may cause damage.

ESD

While ESD protection has been incorporated into the RT214's design, limited board space means additional ESD protection, such as TVS protection, is not provided on the engine's I/O interface. Users are advised to implement appropriate protection measures during integration. The engine is shipped in ESD-safe packaging. Always handle the engine with care outside its packaging, ensuring the use of grounding wrist straps and properly grounded work areas.

Dust and Dirt

The RT214 must be housed in an enclosure that effectively prevents dust particles from accumulating on the lens and circuit board, as such contaminants can degrade performance over time.

Ambient Environment

The following environmental conditions must be met for optimal RT214 performance:

Parameter	Requirement
Operating Temperature	-20°C to 55°C
Storage Temperature	-40°C to 70°C
Humidity	5%~95% (non-condensing)

Thermal Considerations

Electronic components within the RT214 generate heat during operation. Extended continuous use may lead to increased temperatures on components like the CPU, CIS, LEDs, and DC/DC converters, potentially degrading image quality and scanning performance. To mitigate overheating:

Ensure sufficient space is allocated for good air circulation within the design.
Avoid using thermal insulation materials, such as rubber, around the RT214.

External Optical Elements

Do not subject external optical components attached to the engine to any external force. Avoid holding the engine by an external optical component, as this could cause mechanical joints to crack or break due to excessive stress.

Mounting

The following illustrations detail the mechanical mounting dimensions (in millimeters) for the RT214. The tolerance for dimensions is ±0.15mm.

Figure 2-1: Depicts the mounting dimensions, including the overall width (21.5mm MAX), depth (7.30±0.2mm), height (9.0mm MAX), and the location of the Imaging Center and Imaging Central Axis. It also shows a connector (FH35C-13S-0.3SHW) with PIN 1 identified. Mounting holes are specified as M1.4, with a maximum depth of 2mm.

Housing Design

Note: Conduct an optical analysis for the housing design to ensure optimal scanning and imaging performance. The housing design should prevent internal reflections from the aiming and illumination systems from being directed back into the engine, as these can cause issues. Avoid placing highly reflective objects near the engine that might create bright spots in captured images. Using baffles or matte-finished dark internal housing colors is recommended.

Optics

The RT214 utilizes a sophisticated optical system. Improper internal housing design or incorrect window material selection can degrade the engine's performance.

Window Placement

The window must be positioned correctly to allow the illumination and aiming beams to pass through with minimal reflection back into the engine, which could impair reading performance. Two window placement options are available:

Parallel window: This is the primary option for imager engines. The following distance requirements must be met: The maximum distance from the engine housing front to the nearest window surface should not exceed 'a' (0.1mm). The distance from the engine housing front to the furthest window surface should not exceed 'a+d' (where a=0.1mm, d=2mm).
Tilted window: This option is suitable for laser/imager engines. Refer to Table 2-2 for specific distance requirements.

Figure 2-2: Illustrates the concepts of Parallel Window and Tilted Window placement, showing dimensions 'a', 'b', 'd', and 'w'.

Table 2-2: Specifies minimum angles for tilted windows (positive and negative tilt) corresponding to different distances from the front of the engine housing (10mm, 15mm, 20mm).

Window Material and Color

The window material must be clear. Cell-cast plastics or optical glass are recommended, with PMMA and chemically tempered glass being preferred. The selected window material should meet or exceed the specifications in Table 2-3. For clear plastic windows, applying an anti-reflection (AR) coating is advised.

PMMA (Cell-cast acrylic): Offers good optical quality and low cost but requires surface protection due to susceptibility to chemicals, mechanical stress, and UV light. It provides reasonably good impact resistance.
Chemically tempered glass: A hard material offering excellent scratch and abrasion resistance. Unannealed glass is brittle; chemical tempering enhances flexibility and strength with minimal optical distortion. Glass is difficult to cut into custom shapes and cannot be ultrasonically welded.

Table 2-3: Details window specifications, including spectral transmittance (≥90% for PMMA, ≥91% for chemically tempered glass), thickness (0.5-2.0mm), light wavelength (400-780nm), clear aperture (1.0mm to edges), and surface quality (60-20 scratch/dig).

Pay close attention to the light wavelength when using plastic materials. Colored windows are not recommended for scanning barcodes on moving objects.

Coatings and Scratch Resistance

Window scratches can significantly reduce the RT214's performance. Using abrasion-resistant window material or coatings is suggested. Two common coating types are:

Anti-reflection (AR) coatings: Applied to window surfaces to minimize light reflection back into the engine. Multi-layer AR coatings can achieve less than 0.5% reflectance across the 400-780nm wavelength range.
Scratch resistance coatings: These coatings require a hardness greater than 5H and are applied to plastic surfaces to improve abrasion and scratch resistance.

Both tempered glass and plastic windows can be AR coated, with glass being easier and more cost-effective. AR coating specifications require a minimum transmittance of 93% (single-side) or 97% (double-side) within the 400-780nm spectrum.

Window Size

The window must not obstruct the field of view and should be sized to accommodate the aiming and illumination envelopes.

Figure 2-3 (Horizontal): Illustrates the horizontal angular envelopes: Illumination Envelope (58.5°), FOV Envelope (42°), and Aiming Envelope (3.6°). It also shows key dimensions such as 1.95mm, 5.05mm, 7.00mm, 8.70mm, 3.10mm, and 3.89mm.

Figure 2-4 (Vertical): Shows the vertical angular envelopes: Illumination Envelope (68.3°) and FOV Envelope (31.5°), with dimensions 3.40mm, 5.60mm, and 3.89mm.

Figure 2-5: Details the Aiming Envelope (3.6°) with dimensions 3.40mm and 3.10mm.

Roll, Skew and Pitch

Three types of reading angles are illustrated in Figure 2-6: Roll (rotation around the Z-axis), Skew (rotation around the X-axis), and Pitch (rotation around the Y-axis). For detailed technical specifications, consult the RTscan website or a dealer.

Figure 2-6: Visually represents Roll, Skew, and Pitch rotations relative to the X, Y, and Z axes.

Ambient Light

The RT214 performs better in the presence of ambient light. However, high-frequency pulsed light may lead to performance degradation.

Eye Safety

The RT214 does not use lasers; it employs LEDs for its illumination beam. While the LEDs are bright, testing confirms the engine is safe for its intended applications under normal usage conditions. Users should still avoid looking directly into the beam.

Power Supply

Ensure the RT214 is properly connected before powering it on. Always cut off power before connecting or disconnecting cables from the host interface connector to prevent damage from hot-plugging.

Unstable power supplies, sharp voltage drops, or very short intervals between power cycles can lead to unstable performance. Do not reapply power immediately after cutting it off.

When designing, ensure the RT214's input power is fully decoupled. It is recommended to place 22µF and 100nF X5R or X7R ceramic capacitors near the power input pin on the connector. The external input power supply capacitor should be limited to 50µF.
Ensure the input power drops below 0.5V before powering the RT214 on again to prevent abnormal function.

Ripple Noise

To maintain image quality, a power supply with low ripple noise is essential. The acceptable ripple range (peak-to-peak) is ≤100mV.

DC Characteristics

Operating Voltage

Table 3-1 (T=25°C): Specifies the input voltage (VDD) range: Minimum 3.14V, Typical 3.3V, Maximum 3.47V.

Operating Current

Table 3-2 (T=25°C): Details current consumption at VDD=3.3V: Working Current (PEAK 240mA, RMS 138mA) and Standby Current (11.8mA).

Current Waveform Figures

Figure 3-1: Displays the working current waveform.

Figure 3-2: Shows the working current waveform with the aimer turned off.

Figure 3-3: Shows the working current waveform with the illumination turned off.

Figure 3-4: Illustrates the maximum impulse current when the device is powered on, showing a peak of 439mA. It is recommended that the external VDD supply at least 500mA. Ensure cable resistance (Rdc) is controlled within 0.35Ω by using shorter FPC cables and wider power/ground lines. Avoid using long cables, as this can lead to abnormal function.

I/O Voltage

Table 3-3 (VDD=3.3V, GND=0V, T=25°C): Defines the input and output voltage levels for various parameters:

VIL (Except nTRIG pin): Minimum -, Typical -, Maximum 0.8V
VIH (Except nTRIG pin): Minimum 2V, Typical -, Maximum -
VIL (Only nTRIG pin): Minimum -, Typical -, Maximum 2.2V (VDD-1.1V)
VIH (Only nTRIG pin): Minimum 2.9V (VDD-0.4V), Typical -, Maximum -
VOL (Iol=4mA~16mA): Minimum -, Typical -, Maximum 0.4V
VOH (Ioh=4mA~16mA): Minimum 2.4V, Typical -, Maximum -

Note: The high and low level thresholds for the nTRIG pin are dependent on the external VDD. The input low level VIL for nTRIG should be below VDD-1.1V, and the input high level VIH should be above VDD-0.4V.

Timing Sequence

Power Up Timing Sequence

Figure 3-5: Presents a timing diagram illustrating the sequence of signals (VDD, BUZ, TXD, RXD, USB_D+, USB_D-, nTRIG, nRST) during the power-up process. Key timing intervals are indicated: A (bootloader execution time) is 25ms, B (kernel boot time) is 5ms, and C (decoding chip initialization time) is 185ms, totaling approximately 215ms (A+B+C).

Note on Reset: D represents the reset time (300µs). If the Reset signal is not active during power-on, the startup time calculation should commence after VCC_3V3 reaches 3.3V.

Power-off Procedure: Ensure all communication interface data has been transmitted before powering down the device.

nTRIG Signal: The RT214 features a 100K pull-up on the nTRIG signal. During the period between power-on and bootloader execution, the nTRIG signal should not be lowered. If nTRIG is set high before power-on, it must meet the duration of E (0~1ms) as shown in Figure 3-4. Other signals should remain low during power-on to prevent abnormal function.

Figure 3-6: An oscilloscope capture showing the Power Up Timing Sequence for the Serial Interface.

Figure 3-7: An oscilloscope capture showing the Power Up Timing Sequence for the USB interface.

Power Down Timing Sequence

Figure 3-8: Displays the timing diagram for the power-down sequence of signals (VDD, TXD, RXD, USB_D+, USB_D-, nTRIG, nRST). When powering down the RT214, cut off the power and ensure that the levels of TXD, RXD, USB_D+, USB_D-, nTRIG, and nRST signals are kept low.

Interface Pinouts

The RT214 features a 12-pin FPC connector for host communication.

12-pin definition of pinout of RT214:

PIN#	Signal Name	I/O	State	Function
1	NC	-	-	-
2	VDD	-	-	3.3V power input
3	GND	-	-	Power-supply ground
4	RXD	I	-	TTL level 232 receive data
5	TXD	O	-	TTL level 232 transmit data
6	USB_D-	-	-	USB_D- signal
7	USB_D+	-	-	USB_D+ signal
8	NC	-	-	-
9	BUZ	O	-	Beeper output
10	LED	O	-	Good Read LED output
11	nRST	I	-	Reset signal input
12	nTRIG	I	-	Trigger signal input

Note: Ensure your device's TXD is connected to the RT214's RXD, and your device's RXD is connected to the RT214's TXD.

External Circuit Design

Good Read LED Circuit

The circuit shown in Figure 5-1 is used to drive an external LED for indicating a successful barcode read. It involves connecting the RT214's LED output to a transistor (Q1) with associated resistors (R1, R2, R3) and the external LED.

Beeper Circuit

The circuit depicted in Figure 5-2 is designed to drive an external beeper. It connects the RT214's BUZ output to a transistor (Q1) with resistors (R1, R2, R3) and the external beeper.

Trigger Circuit

The circuit in Figure 5-3 provides a signal to trigger a scan and decode session for the engine. The host system can adjust the external circuit and its functions based on application needs. Recommended values are R1 (10K-100K) and R2 (330Ω). C1 is used to suppress mechanical key vibration, with 1nF-10nF ceramic capacitors generally recommended. For ESD protection, an ESD protector (like ED1) can be added. When using an external IO port as a trigger output, ensure high and low levels meet the requirements in Table 3-3. It is recommended to use the default floating or pull-up IO port as the trigger pin. If only a default pull-down IO port is available, refer to the power-on timing sequence in Figure 3-5. When not triggered, the pin must meet the high-level requirements specified in Table 3-3.

EVK (Evaluation Kit)

The Evaluation Kit (EVK) is provided to facilitate testing and evaluation of the RT214. It includes a beeper and beeper driver circuit, an LED and LED driver circuit, trigger functionality, a TTL-232 to RS-232 converter, RS-232 or USB interfaces, and a reserved signal debugging interface, among other features.

For any technical support, please contact support@rtscan.net.