Chapter 1 Overview

1.1 Introduction

The E77-400M22S is a wireless communication module based on ST's STM32WLE5CCU6 SoC. It offers long communication distance, low standby power consumption, strong anti-interference capabilities, rich interface resources, high processing power, and a compact size. It is suitable for the 410.3MHz-493.3MHz frequency band and utilizes industrial-grade high-precision 32.768kHz and 32MHz crystal oscillators. The module requires secondary development by the user and is widely applicable in the Internet of Things (IoT) industry.

1.2 Features

• Communication distance can reach 50m under ideal conditions.
• Maximum transmit power is less than -15dBm, adjustable via software.
• Supports global license-free ISM 410.3MHz-493.3MHz frequency band.
• Features a new spreading factor to support dense networks.
• Supports 1.8V~3.6V power supply; optimal performance is guaranteed with a supply greater than 3.3V.
• Uses 32.768kHz and 32MHz high-precision industrial-grade crystal oscillators.
• Compact 14.0*20.0*2.7mm SMD package, facilitating system integration.
• Industrial standard design, supporting long-term use at -40°C to +85°C.
• Optional dual antennas (IPEX/stamp hole) for convenient user development and integration.

1.3 Application Scenarios

• Home security alarm and remote keyless entry.
• Smart home and industrial sensors.
• Wireless alarm security systems.
• Building automation solutions.
• Wireless industrial-grade remote control.
• Advanced Meter Reading Architecture (AMI).
• Automotive industry applications.

Chapter 2 Specifications

2.1 RF Parameters

2.2 Hardware Parameters

2.3 Electrical Parameters

Chapter 3 Mechanical Dimensions and Pin Definition

Diagram showing the E77-400M22S module's physical dimensions. It includes a top view (14.0±0.1mm width, 20.0±0.1mm length), a side view (2.7±0.1mm height), and a detailed view of the pads with dimensions. An IPX antenna connector is indicated on the top pad view. The pad quantity is 22, and units are in mm.

Note 1: PA6 and PA7 pins are used as internal control RF switches of the module, where PA6 = RF_TXEN, PA7 = RF_RXEN. RF_TXEN=1 RF_RXEN=0 is the transmit channel, and RF_TXEN=0 RF_RXEN=1 is the receiving channel.

Note 2: The PC14-OSC32_IN and PC15-OSC32_OUT pins have been connected to a 32.768KHz crystal oscillator inside the module for users to choose and use in secondary development.

Note 3: The OSC_IN and OSC_OUT pins have been connected to a 32 MHz crystal oscillator inside the module for users to choose and use in secondary development.

Chapter 4 Basic Operations

4.1 Hardware Design

• It is recommended to use a DC regulated power supply with a low ripple coefficient and ensure the module is reliably grounded.
• Pay close attention to the correct connection of power supply polarity; reverse connection can cause permanent damage.
• Verify that the power supply voltage is within the recommended range. Exceeding the maximum value will permanently damage the module.
• Ensure power supply stability; voltage should not fluctuate greatly or frequently.
• When designing the power supply circuit, reserve at least 30% margin for stable long-term operation.
• Keep the module away from components with large electromagnetic interference (e.g., power supplies, transformers, high-frequency wiring).
• High-frequency digital traces, high-frequency analog traces, and power traces should avoid the underside of the module. If routing is necessary, use copper on the Top Layer of the contact part, well-grounded, close to the digital part, and routed on the Bottom Layer.
• Arbitrarily routing wires on the Bottom Layer or other layers when the module is on the Top Layer can affect stray and receiving sensitivity.
• Devices with significant electromagnetic interference nearby can greatly affect module performance. Maintain adequate distance or use isolation/shielding.
• Traces with large electromagnetic interference (high-frequency digital, analog, power) nearby can also affect performance. Maintain distance and consider isolation/shielding.
• If using a 5V communication line, a 1k-5.1k resistor in series is recommended (though not risk-free).
• Avoid TTL protocols with physical layers similar to 2.4GHz, such as USB3.0.
• Antenna installation significantly impacts performance. Ensure the antenna is exposed, preferably vertically upward. For internal installations, use a high-quality extension cable.
• Do not install the antenna inside a metal shell, as it will greatly weaken transmission distance.
• A 200Ω protection resistor is recommended for the external MCU's RXD/TXD pins.

4.2 Software Writing

• Refer to the E77-400M22S routine from the Chengdu Ebyte official website for GFSK modulation/demodulation demonstration.
• Download and consult ST's stm32cubewl library file, using stm32cubemx to generate the protocol stack project.
• Software adjust the internal load capacitance of the crystal oscillator; recommended value: XTAL_DEFAULT_CAP_VALUE=0x0B.
• PA6 and PA7 pins control RF switches: PA6=RF_TXEN, PA7=RF_RXEN. RF_TXEN=1 RF_RXEN=0 for transmit; RF_TXEN=0 RF_RXEN=1 for receive. RF_TXEN and RF_RXEN cannot be both high or low simultaneously.

Chapter 5 Basic Applications

5.1 Basic Circuit

Schematic diagram illustrating a basic circuit for the E77-400M22S module. It shows connections for various pins (PB3, PB4, PB5, PB6, PB7, PB8, PA0, PA1, PA2, PA3, PA4, PA5, GND, ANT, NRST, PA8, PB12, PA10, PA11, PA12, PB2, PB0, PA15, PC13, VDD, SWDIO, SWCLK) to a microcontroller or other components. Power supply (VDD 3V3) and ground (GND) are shown, along with decoupling capacitors (1uF and 10uF).

Chapter 6 Frequently Asked Questions

6.1 The transmission distance is not ideal

• Obstacles in the line of sight attenuate communication distance.
• Temperature, humidity, and co-channel interference increase packet loss rate.
• Ground proximity can absorb/reflect radio waves, leading to poor test effects.
• Seawater strongly absorbs radio waves, making seaside tests less effective.
• Metal objects near the antenna or placement within a metal shell cause significant signal attenuation.
• Incorrect power register settings or excessively high air rates (closer distance) can affect range.
• Low power supply voltage at room temperature reduces output power.
• Poor antenna matching or low antenna quality can be problematic.

6.2 Module is easily damaged

• Ensure the power supply voltage is within the recommended range; exceeding the maximum value will cause permanent damage.
• Check power supply stability; avoid frequent or large voltage fluctuations.
• Use anti-static precautions during installation and use, as high-frequency components are sensitive.
• Avoid high humidity during installation and use, as some components are humidity-sensitive.
• Unless specifically required, avoid operation at extremely high or low temperatures.

6.3 Bit error rate too high

• Co-frequency signal interference nearby requires moving away from the source or changing frequency/channel.
• Non-standard SPI clock waveforms or long SPI bus lines can cause issues; check for interference.
• Unsatisfactory power supply can lead to garbled characters; ensure power supply reliability.
• Poor quality or excessively long extension cables and feeders can cause high bit error rates.

FCC STATEMENT

Important Notice to OEM Integrators

(Reference KDB 996369 D03 OEM Manual v01, 996369 D04 Module Integration Guide v02)

1. Applicable FCC rules:

This device complies with Part 15.231 of the FCC Rules. This module is limited to OEM installation ONLY.

2. Installation limitations:

This module is limited to installation in mobile or fixed applications, according to Part 2.1091(b). Separate approval is required for other configurations, including portable ones (Part 2.1093) and different antenna configurations.

3. Host manufacturer responsibilities (FCC Part 15.31 (h) and (k)):

The host manufacturer is responsible for additional testing to verify compliance as a composite system. This includes showing compliance with Part 15 Subpart B while the transmitter module(s) are installed and operating, ensuring intentional emissions are compliant, and verifying no additional unintentional emissions are present or are compliant with transmitter rules. Guidance for Part 15 B requirements will be provided by the Grantee if needed.

Important Note on Antenna Trace Design:

Any deviation from the defined antenna trace parameters requires notification to Chengdu Ebyte. A Class II permissive change application or a change in FCC ID (new application) followed by a Class II permissive change application may be required.

End Product Labeling

When the module is installed in the host device, the FCC ID label must be visible through a window on the final device or it must be visible when an access panel, door or cover is easily removed. If not, a second label must be placed on the outside of the final device that contains the following text: "Contains FCC ID: 2A8C3-E77400M22S". The FCC ID can be used only when all FCC compliance requirements are met.

Antenna Installation

• The authorized antenna must be used.
• The transmitter module may not be co-located with any other transmitter or antenna.
• Only antennas of the same type and with equal or less gains as shown below may be used with this module. Other types of antennas and/or higher gain antennas may require additional authorization for operation.

In the event that these conditions cannot be met (for example, certain laptop configurations or co-location with another transmitter), then the FCC authorization is no longer considered valid and the FCC ID cannot be used on the final product. In these circumstances, the OEM integrator will be responsible for re-evaluating the end product (including the transmitter) and obtaining a separate FCC authorization.

Information on test modes and additional testing requirements

1) The modular transmitter has been fully tested by the module grantee on the required number of channels, modulation types, and modes; it should not be necessary for the host installer to retest all available transmitter modes or settings. It is recommended that the host product manufacturer, installing the modular transmitter, perform some investigative measurements to confirm that the resulting composite system does not exceed the spurious emissions limits or band edge limits (e.g., where a different antenna may be causing additional emissions).

2) Testing should check for emissions that may occur due to the intermixing of emissions with other transmitters, digital circuitry, or due to physical properties of the host product (enclosure). This investigation is especially important when integrating multiple modular transmitters where certification is based on testing each of them in a stand-alone configuration. Host product manufacturers should not assume that because the modular transmitter is certified, they have no responsibility for final product compliance.

3) If the investigation indicates a compliance concern, the host product manufacturer is obligated to mitigate the issue. Host products using a modular transmitter are subject to all applicable individual technical rules as well as general conditions of operation in Sections 15.5, 15.15, and 15.29 to not cause interference. The operator of the host product will be obligated to stop operating the device until the interference has been corrected.

4) Additional testing, Part 15 Subpart B disclaimer: The device is only FCC authorized for specific rule parts (i.e., FCC transmitter rules) listed on the grant. The host product manufacturer is responsible for compliance to any other FCC rules that apply to the host not covered by the modular transmitter grant of certification. The final host/module combination needs to be evaluated against FCC Part 15B criteria for unintentional radiators to be properly authorized for operation as a Part 15 digital device. The host integrator installing this module must ensure the final composite product complies with FCC requirements through technical assessment, referring to guidance in KDB 996369. For host products with certified modular transmitters, the frequency range of investigation for the composite system is specified by rule in Sections 15.33(a)(1) through (a)(3), or the range applicable to the digital device as shown in Section 15.33(b)(1), whichever is higher. When testing the host product, all transmitters must be operating. Transmitters can be enabled using publicly available drivers. When testing for emissions from the unintentional radiator, the transmitter shall be placed in receive mode or idle mode, if possible. If receive mode only is not possible, the radio shall be passive (preferred) and/or active scanning. This may require enabling activity on the communication BUS (e.g., PCIe, SDIO, USB) to ensure the unintentional radiator circuitry is enabled. Testing laboratories may need to add attenuation or filters depending on the signal strength of any active beacons. See ANSI C63.4, ANSI C63.10 for general testing details. The product under test should be set into a link/association with a partnering device as per normal intended use. To ease testing, the product under test can be set to transmit at a high duty cycle, such as by sending a file or streaming media content.

Manual Information to the End User

The OEM integrator must be aware not to provide information to the end user regarding how to install or remove this RF module in the user's manual of the end product. The end user manual shall include all required regulatory information/warnings as shown in this manual.

Federal Communication Commission Interference Statement

This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.

This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one of the following measures:

• Reorient or relocate the receiving antenna.
• Increase the separation between the equipment and receiver.
• Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
• Consult the dealer or an experienced radio/TV technician for help.

Any changes or modifications not expressly approved by the party responsible for compliance could void the user's authority to operate this equipment. This transmitter must not be co-located or operating in conjunction with any other antenna or transmitter.

Radiation Exposure Statement

This equipment complies with FCC radiation exposure limits set forth for an uncontrolled environment. The device has been evaluated to meet general RF exposure requirement. The device can be used in portable exposure condition without restriction.

List of applicable FCC rules

This module has been tested and found to comply with Part 15.231 requirements for Modular Approval. The modular transmitter is only FCC authorized for the specific rule parts (i.e., FCC transmitter rules) listed on the grant. The host product manufacturer is responsible for compliance to any other FCC rules that apply to the host not covered by the modular transmitter grant of certification. If the grantee markets their product as being Part 15 Subpart B compliant (when it also contains unintentional-radiator digital circuit), then the grantee shall provide a notice stating that the final host product still requires Part 15 Subpart B compliance testing with the modular transmitter installed.

This device is intended only for OEM integrators under the following conditions: (For module device use)

• 1) The authorized antenna must be used, and
• 2) The transmitter module may not be co-located with any other transmitter or antenna.

As long as these two conditions are met, further transmitter testing will not be required. However, the OEM integrator is still responsible for testing their end-product for any additional compliance requirements required with this module installed.

To meet provisions of this section 15.231(a), specific AT commands are input and locked in firmware. And it is triggered by clicking the key in test software during test. Provided the RF module installed in host or end product, it shall employ one switch to manually operate transmitter or equivalent method.

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