External Display for WAHOO KICKR BIKE SHIFT

Code is written for LILYGO T-Display-S3 ESP32-S3 or LILYGO TTGO T-Display ESP32 and displays the following Bluetooth Low Energy (BLE) data:

• Gearing ratio (as set in the wahoo app) and what gears you are currently in. Information (text and graphic) will update when shifting.
• Cycling power (watts and watts per kilogram). Displayed information can be changed (instantaneous power, 3s moving average, 10s moving average) via a button (BOOT) on the device.
• Cycling cadence (RPM - revolutions per minute)
• Cyclist weight (as set in the wahoo app) - Not visible on the display but used to calculate W/kg

Setup & Requirements

You need to install the Arduino IDE to compile and upload the code to the microcontroller. A very good HOWTO can be found here: https://github.com/teastainGit/LilyGO-T-display-S3-setup-and-examples/blob/main/T-DisplayS3_Setup.txt

ESP32 Core for Arduino IDE Version

Code is written for the latest stable version (v3.1.0) and does not work with former 2.x.x as there are some changes to the BLE library. Documentation on how to install the ESP32 Core can be found here: https://docs.espressif.com/projects/arduino-esp32/en/latest/installing.html

TFT_eSPI

Comment and un-comment the following lines in the "..\libraries\TFT_eSPI\User_Setup_Select.h" file depending on which board you use.

#include <User_Setups/Setup25_TTGO_T_Display.h>

#include <User_Setups/Setup206_LilyGo_T_Display_S3.h>

A few things to consider

1. If you have changed the Bluetooth name of your bike (in the wahoo app) you will need to change it also in the code:

// BLE Server name

#define bleServerName "KICKR BIKE SHIFT 720C"

2. Set Display Resolution "170 x 320" for LILYGO T-Display-S3 ESP32-S3 or "135 x 240" for LILYGO TTGO T-Display ESP32

#define RESOLUTION_X 320

#define RESOLUTION_Y 170

3. The graphic should scale depending on the gearing setting, so it will fit the screen. (There are variables to change the rendering if necessary.)

int myGearWidth = (IWIDTH - 35) / (myFrontGears + myRearGears);

#define myGearHeight (RESOLUTION_Y - 60)

#define myGearSpacing -1

#define myGearX 15

#define myGearY 30

Development Notes

1. Debugging: All Status messages during initiation and during connecting process will be displayed on the TFT and in the serial monitor window of the IDE. I tried to comment the code so that it is easier to understand.

2. To identify BLE GATT servies and characteristics use https://www.bluetooth.com/specifications/assigned-numbers/ and if you look at GATT Specification Supplement 5 it describes how to intepret the bytes: https://www.bluetooth.com/specifications/specs/gatt-specification-supplement-5/

3. Scan BLE devices: https://www.nordicsemi.com/Products/Development-tools/nrf-connect-for-mobile

Enter the upload mode for Sketch upload manually.

• Connect the board via the USB cable
• Press and hold the BOOT button (next to RST) , While still pressing the BOOT button, press RST
• Release the RST
• Release the BOOT button
• Upload sketch

Cycling Power Measurement (Power & Cadence)

As mentioned in the GATT Specification Supplement document the Service 0x1818 holds the characteristic 0x2A63. The first UINT16 (unsigned 16-bits integer) holds the FLAGS. In our Case "3C00" (as little-endian) and so we get "00000000 00111100". Section "3.59.2.1 Flags field" in the document tells us which values are beeing submitted:

• Pedal Power Balance Present: False
• Pedal Power Balance Reference: Unknown
• Accumulated Torque Present: True 16
• Accumulated Torque Source: Crank based
• Wheel Revolution Data Present: True 32 & 16
• Crank Revolution Data Present: True 16 & 16
• treme Force Magnitudes Present: False
• Extreme Torque Magnitudes Present: False
• Extreme Angles Present: False
• Top Dead Spot Angle Present: False
• Bottom Dead Spot Angle Present: False
• Accumulated Energy Present: False
• Offset Compensation Indicator : False

So the values in the characteristic are:

Flags field	Instantaneous Power	Accumulated Torque	Cumulative Wheel Revolutions	Last Wheel Event Time	Cumulative Crank Revolutions	Last Crank	Event Time
Mandatory	Mandatory	Optional	Optional	Optional	Optional	Optional	Optional
0 - uint16	1	2	3	4	5	6	7
[0][1]	[2][3]	[4][5]	[6][7]	[8][9]	[10][11]	[12][13]	[14][15]

FONT for ESP32 LCD

• Install selected Google Font
• Install Processing - https://processing.org/download
  • Select "Toools" - "Create Font" and after selecting the font the ".vlw" file will be created in the "\data" folder.
• Covert ".vlw" to binary - https://tomeko.net/online_tools/file_to_hex.php?lang=en
  • copy to clipboard an create a ".h" file and add constructor

  const uint8_t FontName[] PROGMEM = { BINARY };