How to use CC2541 Bluetooth module to communicate with the microcontroller through serial port

1. Overview of CC2541 device

The CC2541 is a power-optimized true system-on-chip (SoC) solution for low energy and private 2.4GHz applications. It makes it possible to build robust network nodes with low overall bill of materials cost. The CC2541 combines the performance of a leading RF transceiver with an industry-standard enhanced 8051 MCU, in-system programmable flash memory, 8kBRAM and many other powerful features and peripherals. The CC2541 is ideally suited for systems requiring ultra-low power consumption. This is specified by a number of different operating modes. Short transition times between operating modes further enable low energy consumption

2. Characteristic parameters of CC2541 chip

The CC2541 is a power-optimized true system-on-chip (SoC) solution for Bluetooth Low Energy and private 2.4GHz applications. It makes it possible to build robust network nodes with low overall bill of materials cost. The CC2541 combines the performance of a leading RF transceiver with an industry-standard enhanced 8051 MCU, in-system programmable flash memory, 8kBRAM and many other powerful features and peripherals. CC2541 on CC2541 CC2541 is very suitable for applications requiring ultra-low power consumption. This is specified by a number of different operating modes. Short transition times between operating modes further enable low energy consumption.

If USB is not enabled on the CC2540 and I2C/extra I/O is not enabled on the CC2541, the CC2541 is pin-compatible with the CC2540 in a 6mmx6mm Quad Flat No-Lead (QFN) 40 package. Compared with CC2540, CC2541 provides lower RF current consumption. CC2541 does not have the USB interface that CC2540 has, and provides a lower maximum output power in TX mode. CC2541 also adds a HWI2C interface.

CC2541 is pin-compatible with CC2533 optimized RF4CEIEEE802.15.4SoC. CC2541 is available in 2 different versions: CC2541F128/F256 with 128kB and 256kB flash memory respectively.

1. Features

(1) Radio frequency

–2.4GHz Bluetooth meets low energy consumption specifications and proprietary RF on-chip system

– Supports controller core data rates of 250kbps, 500kbps, 1Mbps, 2Mbps – Excellent link budget, supports long-distance applications without using external front-end – Programmable output power up to 0dBm

– Excellent receiver sensitivity (-94dBm at 1Mbps), selectivity, and blocking performance

– Suitable for systems that comply with worldwide radio frequency regulations: ETSIEN300328 and EN3004402 Class (Europe), FCCCFR Part 4715 (USA), and ARIBSTD-T66 (Japan)

(2) Layout

– Minimal external components – Reference design support provided

–6mm&mes;6mm Quad Flat No-lead (QFN)-40 package

– Pin compatible with CC2540 (when not using USB or I2C) (ADC)

(3) Low power

– Working mode RX as low as: 17.9mA

– Operating mode TX (0dBm): 18.2mA – Power mode 1 (4μs wake-up): 270μs – Power mode 2 (sleep timer on): 1μs – Power mode 3 (external interrupt): 0.5μs

(4) TPS62730 is compatible with low power in working mode

– RX as low as: 14.7mA (3V supply) – TX (0dBm): 14.3mA (3V supply)

(5)Microcontroller

– High performance and low power 8051 microcontroller core with code prefetching

– In-system programmable flash memory, 128 or 256KB

– 8KBRAM with holdover function in all power modes

–Support hardware debugging

– Extended baseband automation including automatic acknowledgment and address decoding

– Retention of all relevant registers in all power modes

(6) Peripherals

– Powerful 5-channel direct memory access (DMA)

– General purpose timer (1 16-bit, 2 8-bit)

– Infrared (IR) generation circuit

– 32kHz sleep timer with capture function

– Accurate digital Received Signal Strength Indicator (RSSI) support

–Battery monitor and temperature sensor

– 12-bit analog-to-digital converter (ADC) with 8 channels and configurable resolution

– Advanced Encryption Standard (AES) security coprocessor

– 2 powerful Universal Asynchronous Receiver-Transmitter (UART) supporting several serial protocols

–23 general-purpose I/O pins (21&mes;4mA, 2&mes;20mA)

–I2C interface

– 2 I/O pins with LED driver functionality

– Safety device timer

– Integrated high-performance comparator (7) development tools

–CC2541 Evaluation Module Kit (CC2541EMK)

–CC2541 Mini Development Kit (CC2541DK-MINI)

–SmartRF? software

– Provide IAR embedded Workbench?

2. Software features

(1) Compliant Bluetooth 4.0 protocol-compliant stacker for single-mode Bluetooth Low Energy (BLE) solutions

– Full power optimized stack including controller and host

–GAP - central device, peripheral, or broadcaster (including combined roles)

– Attribute Protocol (ATT)/Generic Attribute Profile (GATT)

– Client and server

–L2CAP description

(2) Sample applications and configuration files

– General application for central and peripheral effects of GAP

– Proximity, accelerometer, simple keywords, and battery GATT services

– Supports more applications within the BLE software stack

(3) Multiple configuration options

– Single-chip configuration, allowing applications to run on the CC2541

– for running on an external microprocessor interface

–BTool - Windows (Windows) PC application for evaluation, development and testing

3. Application scope

2.4GHz Bluetooth low energy system

Private 2.4GHz system

Human-machine interface devices (keyboard, mouse, remote control)

Sports and leisure equipment 1 HWI2C interface.

Mobile phone accessories? Consumer electronics

4. CC2541 containing TPS62730

TPS62730 is a 2MHz buck converter with bypass mode

Extend battery life by up to 20%

Reduced current in all operating modes

30nA bypass mode current to support low power mode

RF performance has not changed

Small package allows small solution size

CC2541 controllable

3. Purpose of CC2541 device

Compliant 4.0 protocol-compliant stack for single-mode Bluetooth Low Energy (BLE) solutions

Full power-optimized stack, including controller and host GAP - central device, peripheral, or broadcaster (including combined roles) Attribute Protocol (ATT) / Generic Attribute Profile (GATT) - client and server symmetrical for multi-processing ( SMP) - AES-128 encryption and decryption L2CAP

Sample applications and configuration files for general applications of GAP central and peripheral functions Proximity, accelerometer, simple keyword, and battery GATT services support more applications within the BLE software stack

Multiple configuration options Single-chip configuration, allowing applications running on the CC2541 to interface with a network processor running on an external microprocessor

BTool - Windows PC application for evaluation, development and testing

4. Bluetooth hardware interface design based on microcontroller 1. Introduction to microcontroller C8051

The microcontroller (MCu) is the core of the Bluetooth application system, and its selection will directly affect the performance of the system. C8051F120 is a high-speed SOC microcontroller compatible with 8051 from Cygnal Company. It has high-speed CIP. 51 core, flexible I/O crossbar switch, advanced clock system, JTAG system debugging interface and multi-source reset system. It has excellent performance. The core adopts a pipeline structure and the speed can reach 100MIPS, which is 40 times faster than the ordinary 51. Rich, small size, low power consumption, high integration and easy debugging.

Some of its main features are listed below:

(1) High-speed, pipeline-structured 8051-compatible CIP. 51 cores;

(2) True 8-bit 500ksps ADC with PGA and 8-channel analog multiplexer;

(3) 2-cycle 16&TImes;16 multiply and accumulate engine;

(4) 8448 (8K+256) bytes of on-chip RAM;

(5) External data memory interface that can address 64K bytes of address space;

(6) Hardware-implemented SPI, SMBus/12C and two UART serial interfaces [10l;

(7) 5 general-purpose 16-bit timers;

(8) Programmable counter/timer array with 6 capture/compare modules;

(9) FLASH memory has the ability to be reprogrammed in the system, can be used for non-volatile data storage, and allows on-site firmware updates;

(10) The on-chip JTAG debugging circuit allows non-intrusive (does not occupy on-chip resources), full-speed, in-system testing;

(11) It can work in the industrial temperature range NI (.45"C - +85.c) N with a voltage of 2.7V ~ 3.6V.

(12) C8051F120 is a 100-pin TQFP package.

2. Connection between microcontroller and Bluetooth module

Currently, the most popular HCI connections are via Universal Asynchronous Receiver Transmitter (UART) and Communication Serial Bus (USB). Among them, UART is usually more popular because its performance and data throughput rate are comparable to the USB interface, and the transmission protocol is relatively simple, which reduces software overhead and is a more cost-effective hardware solution.

①Bluetooth module power cord

The voltage manager of the Bluetooth module has a total of 4 inputs, namely Vcc (12), MASTER (28), SW (27) and SW1 (23). Vcc provides the power supply voltage, the typical value is 3.3V; MASTER (28) provides an independent power loop for the UART, which can be the same as the microcontroller logic interface and can be connected to Vcc; the SW (27) signal controls the internal voltage regulator to turn on or shut down. When connecting Vcc (12), MASTER (28), SW (27) and SW1 (23) together, there is no need to consider the power-on sequence of the Bluetooth module.

Figure 1: Peripheral circuit of Bluetooth module

②Data cable and signal cable

The microcontroller C8051F120 has two UARTs, and UART0 is selected here. During programming, UART0 can be assigned to two pins through the crossbar switch settings, such as P3.1 (TXD) and P3.0 (RXD), which are connected to the RXD and TXD of the Bluetooth module respectively. In addition, the microcontroller needs to allocate two additional pins, such as P1.2 and P1.3, which are used as flow control signals CTS and RTS respectively, and are connected to the RTS and CTS of the Bluetooth module respectively. If CTS is 1, the other party is allowed to send, if CTS is 0, the other party is prohibited from sending.

Figure 2: Peripheral circuit of the microcontroller

③Bluetooth module antenna

The ANT pin of the Bluetooth module is connected to a 50-ohm antenna, and the voltage standing wave ratio of the antenna is less than 2:1. In the design of the experimental board for this topic, the microcontroller and Bluetooth module are welded on a PCB board. Since the Bluetooth module uses a flat package and the pins are very dense, it is difficult to solder it directly to the PCB board, and the antenna is also difficult to solder. Therefore, I designed an auxiliary circuit board by myself. First, weld the Bluetooth module to this auxiliary circuit board, and then lead out some pins of the Bluetooth module to be used, and connect the Bluetooth module to the PCB board through the socket, thus making the Bluetooth Module loading and unloading becomes very convenient. The pins derived from the auxiliary circuit board include GND. Ground wire, VCC. 3. 3V, data transceiver lines RXD and TXD, flow control lines RTS and CTS, and enable signal lines. EN, reset signal line. RESET, among which BTEN is the ON signal in Figure 3. In practical applications, it is connected to VCC, and the others are connected to the microcontroller.