BC68F2130 FSK Application Example

Transcription

1 BC68F2130 FSK Application Example D/N: AN0484E Introduction With a focus on the Sub-1GHz RF application area, Holtek has released a range of RF transmitter SoC Flash MCUs, the BC68F2130/BC68F2140 device series. These devices operate in the 315/433/868/915MHz frequency bands and support both OOK and FSK modulation types. The device series also includes a programmable output power function with a maximum power output value of 13dBm. These features make the devices especially suitable for all kinds of remote switches, office automation products and intelligent home wireless control applications. All devices in the series include an integrated frequency synthesizer, a transmission modulation circuit, an RF power amplifier and a Holtek 8-bit microcontroller, thus implementing a simplified wireless transmitter on a single chip. Device features include low power consumption, a high level of functional integration, high RF power and 16NSOP-EP and 24SSOP-EP package types, making them suitable for use in a wide range of related applications. This application example will introduce an FSK modulation signal transmitting using the BC68F2130. Through the program example, users will have a better understanding of how to use the BC68F2130 RF transmitter function library, showing how an FSK RF receiver can receive a data packet correctly. Operational Principle The BC68F2130 includes both an integrated RF transmitter and a Holtek 8-bit microcontroller. This application example mainly introduces the RF transmitter part. Refer to the BC68F2130/BC68F2140 datasheet for more details on the device s other functions. The BC68F2130 RF transmitter includes a frequency synthesizer, a modulator and an RF power amplifier whose structure details are shown in the following block diagram. XOSCIN XOSC FREQ SYNTH PA RFOUT Register Control Signal FIFO Modulator Figure 1 RF Transmitter Structure AN0484E V / 9 April 10, 2018

2 As shown in the above figure, the frequency synthesizer uses an external input frequency source as a reference. It is controlled by the modulator to synthesize the required frequency after which the frequency is amplified by the amplifier (PA) and output. It should be noted that the output pin external circuit should include an impedance matching circuit to the antenna to transmit the signal correctly and with maximum power. Functional Description After understanding the RF signal transmitter basic operational principles, the following will introduce what considerations are required for RF communication. It is important to take these considerations into account as ignoring them may cause communication failure. RF Output Power The RF output power indicates the RF signal intensity, which will affect the quality of the receiving signal. The signal intensity used in different applications may be different. The RF output power generally uses dbm as the measurement unit. The BC68F2130 supports three optional output power levels: 0, 10 and 13dBm. Operation Frequency The device supports two operation frequencies. One is the system frequency which is the crystal oscillator frequency used by the device. The device supports 12 MHz, 12.8 MHz, 16 MHz and 19.2MHz crystal oscillators. The other is the RF frequency, which is the frequency of the wireless communication. The RF frequency may be different for different countries and applications. This device supports 315MHz, 433MHz, 868MHz and 915MHz frequency bands. Modulation Mode There are several modulation modes for wireless communication. The modulation mode used in this example is Frequency Shift Key, abbreviated as FSK. The device outputs the signal state with a lower frequency for data 0 and a higher frequency for data 1 as shown in the following figure. DATA t Frequency Deviation Figure 2 FSK Modulation Mode In the FSK modulation mode, there are two frequencies, a lower frequency and a higher frequency. The frequency deviation is equal to the difference value between these two frequencies divided by 2. AN0484E V / 9 April 10, 2018

3 Transmission Data Rate The transmitting and receiving data rates need to be synchronized regardless of wired or wireless communication. The data rate is the amount of data transmitted per second. The unit is bps which is "bit/s". Data Packet Format In wireless transmission, the transmitted data will be packaged into a specific data packet format, thus reducing the error signal transmission. Different encoding methods can be used to increase successful data transmission. This application example adopts the transmission data packet format of the Sub-1GHz transceiver BC3601, which conforms to the Holtek development requirements. As shown in Figure 3, the transmitted data is composed of the Preamble, the SYNCWORD, the Trailer, the Data and the Cyclic Redundancy Check (CRC). Preamble (12-bit) 0101 / SYNCWORD (6-byte) S47~S40, S39~S32, S31~S24, S23~S16, S15~S8, S7~S0 Trailer (4-bit) 0101/1010 Data (1-byte) D7~D0 CRC (2-byte) C15~C8, C7~C0 Figure 3 Packet Format conforms to the BC3601 Hardware Description The following introduces the application circuits used in this application example, which users can refer to for their own applications. The BC68F2130 Demo Board: In addition to the BC68F2130 main RF transmitter application circuit, an impedance matching circuit and an antenna are also required as mentioned above. Figure 4 BC68F2130 Demo Board Circuit BCE-GENTX-XXX: Includes a battery holder, keys, power switch, power indicator, RF transmit indicator and a firmware update interface. AN0484E V / 9 April 10, 2018

4 Figure 5 BCE-GENTX-XXX Circuit The above two circuit boards are combined together, as shown in Figure 6. This will be convenient for user operation. Figure 6 BCE-GENTX-XXX and BC68F2130 Demo Board Program Example Description Use the HT-IDE3000 simulation development tool to open the program example projects which are provided in this application example. It mainly includes the following files. File Name main.c BC68F21X0_RF_Set.c BC68F21X0_RF_Set.h TX_EnCoder.asm TX_Encoder.inc vector.asm hal_button.c typedef.h Demo code main program Description RF control/initialization related subroutines RF parameter setup - power, external XTAL, FSK, frequency, data rate/fdev RF packet setup subroutine or FIFO mode transmission subroutine RF SYNCWORD parameter setup Interrupt vector table Key related subroutines Common variables and defined values AN0484E V / 9 April 10, 2018

5 The program example is divided into five parts to assist users in quickly understanding their usage. Part 1: BC68F2130 RF parameter setup Part 2: Packet format parameter setup Part 3: Program process introduction Part 4: Considerations Part 5: Receiver recommendations BC68F2130 RF Parameter Setup After the BC68F21X0_RF_Set.h file is opened, users will see that there are 4 defined variables, as shown in the figure. Figure 7 BC68F2130 Basic Parameter Setup 1. Set RF power: There are three optional output power levels: 0, 10, and 13dBm. The required output power defined value is set to 1 while the others are cleared to 0. The RF power default value is 0dBm. In addition, the level variable is used for fine tuning with a default value of 4. It is recommended to be left unchanged. 2. Set RF Freq: Xtal variable is used to set the BC68F2130 external crystal oscillator frequency. It can be set to 120, 128, 160, or 190, which means that the device uses an external crystal oscillator value of 12 MHz, 12.8 MHz, 16 MHz, or 19.2MHz. The Xtal default value is 160 which is 16MHz. The other variable, Freq, is used to set the RF frequency, in units of Hz. If a frequency of MHz is to be used then an input value of should be setup. 3. Set OOK/FSK: The FSKOOK value is set to 1 in this program example to select the FSK modulation mode. 4. Set data rate/fdev: The DATARATE_FDEV variable is used to set the data rate and the frequency deviation. There are five optional combinations in this program example, refer to the following table. Defined Value Data Rate - bps Frequency Deviation - Hz 1 2K 8K 2 5K 20K 3 10K 40K 4 25K 50K 5 50K 18.75K AN0484E V / 9 April 10, 2018

6 Packet Format Parameter Setup In the TX_Encoder.h file, users only need to set the 6 byte SYNCWORD in this program example, as shown in Figure 8. Figure 8 SYNCWORD Setup Values Refer to Figure 3 and following description for the packet format of this example: Preamble: The length is fixed at 12 bits. This is the example setting value. SYNCWORD: The length is fixed at 6 bytes. This is the example setting value. Trailer: The length is fixed at 4 bits. Data: The length is 1 byte, the external four key states are used as the Data low valid nibble and the high valid nibble is 0, together they form a complete byte. CRC16: The Data is operated using CRC16 which is stored in the CRC field. The program example already contains the calculation subprogram. Users do not need to execute another calculation program. The transmitted data will be added after calling the calculation subprogram. In this packet format, note that the Preamble and Trailer field changes are affected by the MSB or LSB bit of SYNCWORD, as shown in Figure 9. The Preamble format is 1010 or 0101 depending upon the SYNCWORD MSB bit. The Trailer format is 1010 or 0101 depending upon the SYNCWORD LSB bit. This program example provides the corresponding steps, refer to the tx_encoder.asm file. Preamble MSB SYNCWORD LSB Trailer Figure 9 Preamble and Trailer Formats Program Procedure Introduction This program example is a remote controller that is applied to four key functions. If no key is pressed the system will enter the ultra-low power consumption mode, Hold Mode. The system will be woken up to transmit the RF signal after a key command is received. The complete flow is shown in Figure 10. Users can consult with the main.c file to get started quickly. AN0484E V / 9 April 10, 2018

7 START INITRF() Wake-up when press any key N press key? Y CheckButtonStatus() Entry Sleep Mode Fill in MRDATA DATA_PRO() FIFO Mode RUN() Y Tx_strobe=0 & key release N Figure 10 Main Program Procedure The following will introduce the main process steps. Step1: System initialization: The system basic setting values are set first. The mcu_initial() subroutine is used to initialize the MCU I/O parameters. The ButtonIO_initial() subroutine is used to initialize the special parameters of the key related subroutines. The INITRF() subroutine is used to initialize the RF parameters which include the modulation mode, output power, RF frequency, data rate, etc. The transmission mode is set as a Simple FIFO Mode. The InitTBx () subroutine is used to initialize a 2ms timer reference timing, which can be used for the main program state switching and key detection. Figure 11 Initialization Step2: Detect whether a key is pressed or not. If any key is pressed, then set SENDFLAG=TRUE. Step3: The key states are updated to MRFDATA. Step4: Data pre-processing. The DATA_PRO subroutine will be called and the data is shifted according to the data length or address length. Step5: Transmit RF signal. The FIFO_RUN subroutine will be called, the FIFO Mode is executed to transmit a data packet. AN0484E V / 9 April 10, 2018

8 Figure 12 Main Program Process Step 3~5 Step6: After the packet has been transmitted, determine whether _tx_strobe=0 and if the key is not pressed. If yes, set sleep_f=true to force the system to enter the HALT mode. Figure 13 Main Program Process Step 6 Step7: Wait for a key to be pressed. Go back to Step1 and execute the complete process again after a key has been pressed. Considerations If the BC68F2130 enters the Deep Sleep (PWRC=0x03) mode, it can be woken up in two ways, either from port A or from a Time Base 0 interrupt. When the system is woken up from the Deep Sleep mode, the program will resume execution from 0000h. PWRC should be set to 0x00 and the MCU related registers will need to be reinitialised by the F/W. This means to restart execution from Step1. Receiving Recommendations To receive an RF signal in this example, it is recommended to use the Holtek Sub-1GHz transceiver BC3601 as the receiver. Refer to the following website for the BC3601details. Program Example BCM-68F2130-X02-FSK _43392_FIFO Mode_V06.7z Conclusion This application example has introduced how to use the device for transmitting an FSK RF signal. For assistance during programming, users can obtain a simple program example from the Bestcomm RF Electronics Inc. AN0484E V / 9 April 10, 2018

9 Versions and Modify Information BC68F2130 FSK Application Example Date Author Issue and Modify Information 徐鴻文 (Harry Hsu) 何信智 (Walers Ho) First Version Reference Files 1. Reference file: BC68F2130/BC68F2140 Datasheet. 2. BC68F2130/2140 OOK/FSK RF Transmitter Flash MCU Application Guidelines. (Holtek D/N: AN0430E) 3. For more information, refer to the Holtek official website Disclaimer All information, trademarks, logos, graphics, videos, audio clips, links and other items appearing on this website ('Information') are for reference only and is subject to change at any time without prior notice and at the discretion of Holtek Semiconductor Inc. (hereinafter 'Holtek', 'the company', 'us', 'we' or 'our'). Whilst Holtek endeavors to ensure the accuracy of the Information on this website, no express or implied warranty is given by Holtek to the accuracy of the Information. Holtek shall bear no responsibility for any incorrectness or leakage. Holtek shall not be liable for any damages (including but not limited to computer virus, system problems or data loss) whatsoever arising in using or in connection with the use of this website by any party. There may be links in this area, which allow you to visit the websites of other companies. These websites are not controlled by Holtek. Holtek will bear no responsibility and no guarantee to whatsoever Information displayed at such sites. Hyperlinks to other websites are at your own risk. Limitation of Liability In any case, the Company has no need to take responsibility for any loss or damage caused when anyone visits the website directly or indirectly and uses the contents, information or service on the website. Governing Law This disclaimer is subjected to the laws of the Republic of China and under the jurisdiction of the Court of the Republic of China. Update of Disclaimer Holtek reserves the right to update the Disclaimer at any time with or without prior notice, all changes are effective immediately upon posting to the website. AN0484E V / 9 April 10, 2018