GoRail_Pager

A device for receiving and showing POCSAG formatted ChinaRail "LBJ" message which has the meaning of train arrival alert, as well as repeating it through MQTT and logging on local MicroSD card. The project is based on TI CC1101 RF solution, ESP8266 Wi-Fi solution and STM32F103C8T6 microcontroller. Firstly, receive and decode the 2-FSK modulated digital baseband raw data using CC1101. Besides, parse the raw data according to the POCSAG formate regulations. Finally, show the message and do some post processes. On the one hand, show the message on an tiny 0.96"OLED displayer, on the other hand we publish it through MQTT and log it to a text file which is stored on local MicroSD card. This project is the practical and extended version of project "CC1101_Rx_LBJ". (See git@github.com:XieYingnan-Hideo/CC1101_Rx_LBJ.git)

Basic infomation

• Project Name: GoRail_Pager
• Revise version: V1.0
• Created date: 2020-8-3
• Author: Xie Yingnan (xieyingnan1994@163.com)

Hardware requirements

0. CPU

ARM Cortex-M3 STM32F103C8T6

1.TI CC1101 RF solutioin(Operated on STM32F103 SPI2)

fCLK = 9MHz

Function	MOSI	MISO	SCLK	CS	IRQ(GDO2)
Pin	PB15	PB14	PB13	PB12	PB0

2.MicroSD Card (SPI mode, on STM32F103 SPI1)

fCLK = 36MHz

Function	CMD(3)	DAT0(7)	CLK(5)	CD/DAT3(2)
Pin	PA7	PA6	PA5	PA4

3.SPI Flash(W25Q16, on SPI1 also)

For storging:

• Chinese GB2312-1980 16x16 dot matrix data, utilized by OLED screen.
• Splash screen 128x64 dot matrix data.
• Unicode<->GBK codepage converting pairs, used by FatFS, when enabled Long File Name support.

SPI Flash shares same SPI port with SDcard. fCLK = 36MHz

Function	MOSI(5)	MISO(2)	SCK(6)	CS(1)
Pin	PA7	PA6	PA5	PC13

4.IIC Bus

Three devices share the same IIC bus. The time sequence of bus is software simulated.

• 0.96" OLED SSD1306
• RealTime Clock DS3231
• EEPROM AT24C04 (Capacity: 512 bytes)

Function	IIC_SCL	IIC_SDA
Pin	PB4	PB6

5.ESP8266 utilized serial port

Function	UART2 Tx	UART2 Rx
Pin	PA2	PA3

Pattern: 115200 bps, No parity, 8 bits, 1 stopbits

6.Serial Port( For debug info print and convey command strobes)

Function	UART1 Tx	UART1 Rx
Pin	PA9	PA10

Pattern: 115200 bps, No parity, 8 bits, 1 stopbits

7.Indicators(LED, Buzzer)

Function	Pin on MCU
STATUS	PA1
Buzzer	PA0

8.Single Key(short/long press holds different function)

Function	Pin on MCU
KEY_CFG	PA8
When key is on, pin of mcu is pulled to ground.

Details

1.About the Rx procedure and cofiguration of CC1101

The train arrival alerting message is transmitted by locomotive on 821.2375MHz using 2-FSK modulated POCSAG formate. The FSK frequency deviation direction of LBJ systems on locomotive is obeying POCSAG standard. i.e. F+f signifies logical 0, and F-f signifies logical 1. It is exactly reversed to the FSK pattern that CC1101 holds. CC1101 regarding F+f as logical 1 and F-f as logical 0. So we need to do bit reverse operate for receiving LBJ message correctly. The implement method is: change sync code from 0x15D8 to its bit reversed value 0xEA27 and make raw data bit reversed before POCSAG parsing.

Notes: value 0x15D8 is the lower 16bits of standard POCSAG sync code 0x7CD215D8, for CC1101 does not support 32-bit sync code, we only intersect its lower 16 bits.

According to the standard TB/T3504-2018, LBJ systems on locomotive publish two kinds of message on two POCSAG address: 1234000 and 1234008. The former POCSAG message contains traincode, train speed and milesmark that the train just passed. The latter POCSAG message just for time sync utility. The structure of two messages are listed as following chart.

Train arrival alert @ 1234000
576bits preamble+32bit sync(0x7CD215D8)+1 Address codeword(4 bytes)+3 Message Codeword(12 bytes)+3 IDLE Codeword(12 bytes)

Train arrival alert @ 1234008
576bits preamble+32bit sync(0x7CD215D8)+1 Address codeword(4 bytes)+1 Message Codeword(4 bytes)+5 IDLE Codeword(20 bytes)

We can summerize that we only need to receive bytes size of 16(containing 1 Address codeword and 3 Message codeword), the packet size of CC1101 is set to 16, with fixed length mode.

CC1101 receiving package pattern
16 bytes of preamble+16bit sync code (0xEA27)+16bytes of payload(containing 1 address codeword and 3 message codeword)

CC1101 shoud be configured an follow:

CRC Filtering	Package mode	Sync word	Preamble length	FSK Freq deviation
OFF	Fixed length, 16bytes	0xEA27	16 bytes	4.5kHz

2.About the command strings

The operating commands is conducted via serial port, debug and status information of the whole POCSAG parsing procedure is printed via serial port as well. Command strobes to oprate are listed as follow. Each command string should be followed by a Windows-style newline!(aka. CR+LF).

Command string	Function
$	Show this help tips again
$$	List current settings
$V	Show version information
$SAVE	Save settings to EEPROM
$RESTORE	Restore settings to default values
$F=xxx.xxxx	Setting RF Frequency to xxx.xxxx MHz
$EN9X=x	Toggle enable receive 9xxxx traincode
$WLANCFG=x	0:Airkiss,1:SmartConfig
$MQTT="Broker","PubTopic","SubTopic"	Setting MQTT Broker, topic to publish, topic to subscribe
$SN=str	Setting serial number to str
$DESC=str	Setting string descriptor to str
$RTC=yyyy-mm-dd-hh-mm-ss	Setting RTC time

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End of file (Edited by XieYingnan)