#bluetoothchip

In today's interconnected world, Bluetooth technology meets not only audio transmission needs but also plays a key role in data transfer. The KT1025A chip offers excellent Bluetooth data transmission features, supporting two main modes: BLE and SPP.

BLE Transparent Transmission: A Power-Efficient Solution

Designed for low-power applications, BLE is ideal for devices requiring long operation times with minimal power consumption. KT1025A supports standard BLE data transmission, ensuring stable connections and data interaction between devices. This makes it a top choice for smart home and health monitoring devices.

SPP Transparent Transmission: A Classic and Reliable Option

Based on the classic Bluetooth protocol, SPP provides higher data transfer rates and stability. It's perfect for applications needing fast and reliable data transmission, such as industrial control and medical data collection.

Flexibility and Reliability in Data Transmission

Whether using BLE or SPP mode, KT1025A ensures efficient and reliable data transmission. The built-in protocol stack handles the complexities of Bluetooth connections, allowing developers to focus on application development.

Practical Application Cases

In smart home systems, KT1025A can connect various sensors and controllers via BLE for seamless communication. In medical devices, SPP mode can transmit high-precision monitoring data, ensuring accuracy and timeliness.

Conclusion

Introduction When developing Bluetooth speakers with Jieli’s audio SoCs, adding custom prompt tones often brings up a few common issues – popping noises during power on/off, unsupported audio formats, etc. This guide walks through these issues and their solutions using the Jieli AC696N development board.

1. Pop/click noise when playing prompt tones during power on or off

First, listen to the original prompt tone file – is the noise already in the audio itself?

On the development board, the SDK code already includes the following two lines to handle this (add them if missing):

// Power on: disable PA before ramping up

// Power off: disable PA before shutdown

Explanation: When the speaker is powered on or off, the amplifier (PA) and speaker can produce a pop/click sound – this is normal behavior. The solution is to disable the power amplifier before the power‑on sequence, and also disable it before shutting down. The SDK example has these lines written by default. During debugging, you can verify whether the pop disappears after adding them.

2. Added prompt tones in different formats – MP3 works, but WTG doesn't

Double‑check the file format – don’t accidentally mix up extensions.

For WTG format, you need to enable the corresponding codec in the configuration tool.

Different tone formats require different encoder support. Enable the codec for WTG if you really need it. Recommendation: Stick with MP3 for prompt tones – it’s simpler and works out of the box.

1. Introduction

The JL AC696N development board comes with predefined prompt tones. Since developers often need to add their own tones, this guide uses the AC6966B chip as an example to explain how to add custom prompt tones step by step.

2. Detailed Instructions

2.1 Configuration Tool

Custom prompt tones need to be added via the configuration tool. Typical path: ac696n_soundbox_sdk_v1.7.0_patch01_dev_board_v0.0.2\cpu\br25\tools\soundbox\standard

Open the configuration tool → select “Prompt Tone Configuration” → click “Add Prompt Tone” → click “Open”.

After clicking “Open”, choose your custom tone file – the tool will auto‑fill the file path.

Click “Save” – the configuration tool part is now complete.

2.2 Adding the Custom Tone File

Download or create your own tone file (e.g., water.mp3 or .wav). Add the file to the extra_tones folder (follow the same structure as existing tones). Use an English name for the file (e.g., water.*).

2.3 Code Modifications

In tone_player.h, add the custom tone name and path following the existing pattern. Example: #define TONE_RES_ROOT_PATH "tone/water.*"

In tone_table.c (inside the const char *tone_table[] array), add a new entry: [IDEX_TONE_WATER] = TONE_RES_ROOT_PATH"tone/water.*", where water matches your file name.

2.4 Playing the Tone

After the above steps, use the function from tone_player.c to play the tone. Example: tone_play(tone_table[IDEX_TONE_WATER], 1)

Summary

That's all the modification needed. The new tone can be triggered with a simple API call. This approach works on the AC696N series and similar Jieli audio SoCs.

Issue A customer is developing TWS paired speakers using the Jieli AC696N development board. They need to implement a “button-triggered pairing” function, but are unsure which IO pin to connect the button to and how to configure it in the code.

Analysis & Reproduction When reviewing the Jieli AC696N TWS paired speaker example project, we found that pairing is typically triggered by an AD key or a regular GPIO key. The example project reserves the pairing button logic, but does not explicitly state the hardware connection or software configuration mapping. The correct setup requires cross-referencing the schematic diagram and the key scan module in the code.

Solution Open the TWS paired speaker example project and locate the key configuration section:

Hardware connection: It is recommended to connect the pairing button to PB4 (which is defined as an AD key channel in the Jieli AC696N factory firmware). Different buttons are distinguished by their AD sampling values.

Code configuration: In adkey_table.c (or the user key configuration table), find the macro KEY_TWS_SEARCH_REMOVE_PAIR (pairing function). Bind this macro to the specific AD key value.

Modification example: In the key mapping array, set the trigger event of the corresponding AD key to KEY_TWS_SEARCH_REMOVE_PAIR, and ensure the button press duration meets the default pairing trigger condition (e.g., long press for 3 seconds).

After completing the configuration, compile and burn the firmware. The button will then trigger TWS pairing.

Introduction

GPIO configuration seems simple, but there are plenty of cases where things go wrong. If the drive strength isn't set correctly, an LED might be too dim or not light at all. Without proper pull-up/pull-down configuration, button detection can be erratic. The most troublesome is the USB pin—it might default to a regular GPIO, and if you forget to switch its function, your PC won't recognize the device.

The JL JieLi AC696N's GPIOs are quite versatile, with three drive strength levels (normal, strong, super strong) and various APIs. However, these functions are scattered throughout the documentation, and you often have to search for a while when using them. I've gone through the common GPIO configurations on the AC696N development board and organized them into a table, so you can quickly look them up when writing drivers.

I. GPIO Operating Modes

Input Mode: Can be configured as floating, pull-up, pull-down, or analog (for ADC). In input mode, output is disabled. The I/O status can be read via the input data register. Pull-up and pull-down input are straightforward—the default level is determined by the pull-up or pull-down. Floating input level is uncertain and depends entirely on the external input. Analog input is used for ADC sampling.

Output Mode: Output high/low level. Drive strength has three levels: normal, strong, and super strong.

Direction: Input, output. No open-drain.

Pull-up/down: All I/Os have pull-up/down resistors. Fixed resistance values, but differ between chips and pins (check datasheet). Pull-up/down only available in input mode.

Level: Output high (voltage close to VDDIO), output low (equivalent to ground, current sinking).

Drive strength: Normal, strong, super strong. Only very few I/Os support super strong.

State: Digital or analog. Analog state is used for AD detection in input mode.

Reading: In digital input mode, you can read the I/O voltage level. The voltage applied to an I/O must not exceed VDDIO; otherwise, reverse current may affect other I/Os.

II. Core API Function List

III. Special Pin: USB DP/DM

USB pins may default to regular GPIO. To switch them to USB function, call:usb_iomode(0); // parameter 0: switch to USB function

IV. Important Note

The output level of a GPIO is determined by the VDDIO supply voltage. If you need a specific I/O to output 3.0V, you must set the VDDIO supply to 3.0V.

Summary Memorize these few GPIO APIs, and you'll be covered for most tasks. A few common pitfalls:

USB pins: don't forget to call usb_iomode(0) to switch to USB function, otherwise the PC won't recognize the device.

ADC input pins: remember to use gpio_set_die() to disable digital function, otherwise readings will be inaccurate.

Drive strength: choose according to your needs. For driving an LED, strong drive is unnecessary; normal drive works fine and saves power.

Introduction

The serial port is truly the "eyes" of a developer – that statement is no exaggeration. In embedded debugging, if you can't get logs out, it's like working blindfolded.

The UART configuration on the JL Jieli AC696N is quite flexible. The debug print pin can be mapped arbitrarily, and the baud rate can be pushed up to 1M, making debugging very smooth. However, many beginners overlook one point: the serial port can not only output logs, but also connect to a PC tool for online tuning of audio effects. Parameters like EQ and DRC can be adjusted in real time without recompiling and flashing – you can hear the effect immediately.

After tinkering with the AC696N development board, I've sorted out the configuration for both functions so I don't have to dig through the code every time.

I. Configuring Serial Print

In the board-level configuration header file (e.g., board_ac696x_demo_cfg.h), locate the UART0 configuration.

Modify the following macros:#define TCFG_UART0_ENABLE ENABLE_THIS_MOUDLE // Enable #define TCFG_UART0_TX_PORT IO_PORTA_05 // TX pin (changeable) #define TCFG_UART0_BAUDRATE 1000000 // Baud rate (1Mbps)

In app_config.h, control the master print switch and verbosity level.

II. Implementing Online Tuning (No Recompilation Needed)

In lib_system_config.c, enable the effect tool and UART communication:#define TCFG_EFFECT_TOOL_ENABLE ENABLE_THIS_MOUDLE #define TCFG_COMM_TYPE COMM_UART

Specify the UART TX/RX pins for debugging.

Use the PC tool provided by Jieli to connect, and you can adjust EQ, DRC and other audio parameters in real time – the effect is immediate.

III. UART Communication Demo

The SDK provides a uart_test.c example that shows how to initialize an independent communication UART for data sending/receiving, which is very suitable for communicating with external MCUs or modules.

Summary

For serial print, I recommend setting the baud rate directly to 1M. The logs will stream quickly and debugging won't stutter.

The online tuning feature is a highlight of the Jieli solution. It's extremely efficient when developing audio products – tuning parameters while listening to the effect is far more efficient than modifying code, flashing, and listening repeatedly. It's best to use two separate UARTs for debug prints and tuning to avoid log messages interfering with tuning commands.

Introduction

The BLE function of the KT1025A Bluetooth chip supports connection passcodes. By default, the passcode is fixed at 6 digits, and its length cannot be changed. In the default program, the passcode is set to 123456. Please note that each digit must be in the range 0–9 and must not exceed this range.

However, it is important to note a limitation of BLE: even with a passcode set, certain apps may bypass it.

Therefore, it is recommended to implement an interactive encryption mechanism between your app and the Bluetooth chip after a connection is established. For example, after a successful connection, the app can send a data frame to the Bluetooth chip, which then parses and replies according to a predefined protocol. If no correct reply is received, the device can be considered unauthorized.

AT Command Instructions

Set the passcode Command:  AT  +BN  Format:  AT  +BN[passcode]  (up to 6 digits) Example:  AT  +BN889988

Restore factory settings If you forget the passcode, you can reset the chip to factory defaults using: Command:  AT  +CW

Power-on notification When powered on, the chip will automatically report the current BLE connection passcode in the format:  TN  +[passcode]  Example:  TN  +889988

Query the passcode manually You can also actively query the current passcode. Refer to the example below:

Summary

While the KT1025A supports BLE connection passcodes for basic security, developers are encouraged to add an additional layer of protection through custom encryption after connection. This helps ensure that only trusted apps can communicate with the device.

Special Notes:

The input voltage on the VBAT power pin must not exceed 5.0V.

The voltage on the LDO_IN charging input pin must not exceed 5.5V.

A capacitor placement to ground must be reserved for LDO_IN.For speakers or headphones using the internal soft power-on/off solution, please use the PBI pin (low-level wake-up) for the power button.

To ensure product safety and reliability, please use batteries with protection circuits.

Test points must be provided for the programming pins (VBAT, USBDM, USBDP, VDDIO, VSSIO).

Note: The QFN package chip is small, which is not conducive to programming via test fixtures or manual methods. It is recommended to first mount the chip, then program it via PC.

1. Circuit Design Guide

1.1 Crystal Oscillator Selection Guide

Due to Bluetooth's high requirement for frequency offset, the quality of the crystal oscillator is crucial for Bluetooth performance. Consistency and stability of the crystal oscillator must be ensured during selection. The frequency deviation of the crystal oscillator must be ≤ ±10ppm, and a load capacitance (CL) of 12pF is recommended.

Recommended model:  If using crystal oscillators from other models, testing and verification are essential.

1.2 DCDC Selection and Circuit Description

① If the power consumption of the chip's internal LDO mode is acceptable for the application, the external DCDC can be omitted.

② DCDC chip selection: The switching frequency must be greater than 2M, output voltage 1.26V.

③ Use 1% precision resistors for DCDC feedback resistors R2 and R3.

Schematic is as follows: