TI EK-TM4C123GXL Launchpad, reading IBUS signal from FS-iA6B receiver, converts to UART1 U1 TxD to control trolling engine speed/forward-backward, and direction servo actuator.

PB0 - U1RxD : Flysky receiver IBUS through 5 - 3.3V level shifter PB1 - U1Txd : RC UART1 output, 0x00 - 0xFF to RC manually control trolling motor speed PB4 - PWM : RC PWM output, trolling direction servo actuator

Brief

ibus is a Flysky RC receiver protocol

___KEYWORD - i-bus, FLYSKY, UART, TM4C123GXL , PWM

Library Feature

• Receive RC data in UART1 RxD
  • 1000 - 2000
• Software fail-safe

Dev environment

• Keil MDK 5.32
• Keil MDK Legacy
• TivaWare
• FLYSKY Transmitter & Receiver
  • FS-i6, FS-iA6B, FS-A8S (fail-safe X)

FLYSKY ibus protocol

• The ibus protocol is one of RX protocols developed by Flysky
• half-duplex
• Control multiple servos and motors using a single digital line.
• Support 14 channels
• New value can be read every 7ms
• The values received for each channel are between 1000 and 2000, 1-2ms pulse width
• The ibus requires a dedicated hardware serial (UART) port on microcontroller
  • UART RX required
  • 115200 baud
  • 8N1
• Data frame
  • 32 bytes
  • Structure
    • Example set of 32 bytes

      20 40 DB 5 DC 5 54 5 DC 5 E8 3 D0 7 D2 5 E8 3 DC 5 DC 5 DC 5 DC 5 DC 5 DC 5 DA F3
      

    • Section

      Protocol length	Command code	CH1	CH2	CH3	...	CH14	Checksum
      0x20	0x40	0xDB 0x05	0xDC 0x05	0x54 0x05	...	0xDC 0x05	0xDA 0xF3

  • Little Endian

    ibus data	HEX	DEC
    CH1	0x05DB	1499
    CH2	0x05DC	1500
    CH3	0x0554	1364
    ...	...	...
    CH14	0x05DC	1500
    Checksum	0xF3DA

  • Checksum calculation
    • 0xFFFF - (sum of previous 30 bytes)

Example

ibus.h

• UART1 Channels

/* User configuration */

#define IBUS_USER_CHANNELS		6		// Use 6 channels

lpvdebug.h

#define DEBUG true // change it to false for deployment, UART1 is used

main.c

• Only contain ibus things

#include "ibus.h"

// variables to store ibus data
uint16_t ibus_data[IBUS_USER_CHANNELS];

U1RX - PC4 U1TX - PC5

Us PC4 as IBUS inputs

Do not use pins PB0, PB1 as U1RX, U1TX as they are NOT 5V tolerant.

TI EK-123GXL launchpad +5V, 23mA to 323 mA output FS-iA6B 4-6.5V DC, current??

Channel 1 - right up/down joystick - forward full speed and backward full speed (0xFF to 0x00) Channel 2 - right left/right jystick - left/right duty cycle 1% left most to 99% right most

-- program using state machine for receiver 0x20, 0x40 ..... (rest 30 bytes)

==================================================

Date 1/13/2024 FS-i66B iBUS for Sensor iBUS, using software UART, TivaWare SoftUART utilities is used. PC6 (half-duplex, PC6 is connected to Sensor iBUS)

Pins used: UART0 PA0-U0RX, PA1-U1TX; PC4-U1RX, PC5-U1TX; PC6-U3RX, (PC7-U3TX) PC7 is not used for U3TX, therefor, for testing purpose, PC7 is used to program as softURT TX

1/13/2024 8:56pm tested, softUART is working

====================================================== 1/14/2024 FS-i6AB iBUS Sensor RX

hardware connection: +5V, Gnd,
Servo iBUS Signal - TI launnchpad PC4 - U11RX Sensor iBUS signal - TI launchpad PC6 - U3RX - half duplex

SoftUART Tivaware Utilieis

SWA - UP 1000, down 2000 - UP: mission selection; DOWN - Color selection SWB - UP 1000, middle: 1500: Down 2000 SWC - UP 1000, Middle: 1500; Down 2000 SWD - UP: 1000 - Manual Driving LPV; DOWN: 2000 - Automatic KEYB - not pressed 1000; pressed: 2000: confirm of mission/color selection

They are programmed in i-FS6S RC transmitter as: SWA - Channel 5 SWB - Channel 6 SWC - Channel 7 SWD - Channel 8 KEY 1 - channel 9 KEY 2 - channel 10

=========================================== PA2, PA3, PA4, PA5, PA6, PA7 available to Jetson Nano

PA7 - auto or manual PA7 = '1': Auto; '0':Manual PA6 - failsafe MUX ='0': RC link is good; =1 RC link is lost

UART PC4 - U1RxD : Flysky receiver IBUS through 5 - 3.3V level shifter (not needed) DO NOT USE PB0, PB0 is not +5V tolerant PC5 U1Txd : RC UART1 output, 0x00 - 0xFF to RC manually control trolling motor speed PB4 - PWM : RC PWM output, 1.5ms to stop motor when RC signal is lost

UART3 PC6 - Sensor IBUS signal

UART3 PC7 - Jetson RxD interrupt

PC4 - Servo IBUS Signal,PC5 - Motor control ,PC6 - Sensor ibus Signal, PB4 - 1.5ms failsafe to stop motor

A binary containing mission/auto-manual/color is also sent to Jetson Nano through a serial port: A/M MMM CC 6 bits, bit 7 (A/M) bits 6-4 (mission selectin), bit 3-2 (color selection) PD7 cannot be used as GPIO unless it is unlocked first before it is programmmed (datasheet page 218).

=========================================== Flysky iA6S transmitter display message:

format: // encoded rpm; 1xxxx/2xxxx - manua/auto; xx M xx mission number 1-8; xxxx C - color 0-3 xxxx K x K=0 Key 2 not pressed K=1 Key 2 pressed This is for confirm the selection of mission sand color

=========================================================== Wire connections:

iA6B Receiver Jetson Nano Ti Launchpad 74LS 157 Multiplexer iBUS Servo Signal ====> PC4 - U1RXD

iBUS Sensor Signal <====> PC6 - U3RxD - half duplex SoftUART

                             U1RxD - pin 10      <=====     PC7 - U3TxD - mission/color/LPV Mode
			 
							PB4 - PWM1                                          1I0 - pin 4    failsare, 1.5 ms to stop MDS motor driver
																	                           not used

PA7 - auto/manual MUX PA6 - RC link good/bad MUX PA5 - auto beacon PA4 - manual beacon

Left Joystick: Channel 2 - Forward/backward motor driver control Right Joystick: Channel 0 - Left/Right Rotational servo motor

Schematic

TI Launchpad mapping