How to connect Bluetooth gamepad to the LEGO hub directly using a word blocks program.

In this article, you’ll learn how to connect a Bluetooth gamepad to the SPIKE Prime or Robot Inventor hub without lag but with Word Blocks/Scratch. We use an extra piece of hardware, the LMS-ESP32, to convert the Bluetooth signals to a LEGO LPF2 sensor format.

Bluetooth Gamepad as a LEGO sensor in Word Blocks

In a previous post, we showed how to connect a PS4 or Nintendo gamepad to the new LEGO Robot Inventor or SPIKE Prime hubs using Python on the LEGO hub. That post gives some background on the different types of Bluetooth supported by LEGO hubs.

In this how-to guide, we use the  LMS-ESP32 board flashed with a new firmware that presents the LMS-ESP32 board as a standard sensor. We ‘fool’ the Large Hub into thinking it is a LEGO Distance sensor. The name of this specific firmware is Bluepad32. It is open-source and Arduino-based.

Next, we created several MyBlocks to read the two analog joysticks, the D-Pad, and all the buttons on a gamepad. And there is more! We have experimental support for driving NeoPixel LEDs and Servo motors connected to the LMS-ESP32 from the Word Block environment. Read about this near the end of this blog.

Hot Rod controlled by lag-less Bluetooth Gamepad in Word Blocks

The video below shows the Hot Rod model controlled by a Nintendo Gamepad. A PS4 gamepad works too. The program runs on the LEGO hub and is written in Word Blocks.

Step-by-step guide for programming Gamepad direct link in LEGO Word Blocks

How the Bluetooth gamepad Word Blocks template works

The MINDSTORMS word block environment does not allow for low-level reading of a LEGO Sensor. We provide a BluePad32 Word Blocks template that implements all the MyBlocks needed for working with the BluePad32 firmware. The template contains a simple test main loop. You can replace the loop with your own main loop. In MINDSTORMS Word blocks you can not copy MyBlocks from one program to the other, consequently, we use a template program from which you can start your own implementation.

Gamepad MyBlock

The gamepad MyBlock reads the gamepad status in the global variables gp_x, gp_y, gp_rx, gp_ry, gp_buttons and gp_dpad.  When the port-parameter is left empty, the default port will be Port A.  Otherwise, use a single character A-F to configure the port to which the LMS-ESP32 is connected.
The table below shows the definition of the global gamepad-related variable.

Variable	Mode, word	Description
gp_x	M0, word 0	Gamepad left axis X
gp_y	M0, word 1	Gamepad left axis Y
gp_rx	M0, word 2	Gamepad right axis x
gp_ry	M0, word 3	Gamepad right axis y
buttons	M0, word 4	Button status A=2, B=1, X=8, Y=4, left shoulder=16, right shoulder=32, left trigger=64, right trigger=128 analogue left stick= 256, analog right stick=512
dpad	M0, word 5	Dpad status up=1, down=2, right=4, left=8

When multiple keys are pressed simultaneously, the value read from the button or dpad variables is the sum of the corresponding values of the buttons pressed. Since there is no Bitwise or operator in Word Blocks, we added a MyBlock to check for a specific key pressed.

NeoPixels and Servo motor MyBlocks (experimental)

Up to 4 servo motors can be connected to the LMS-ESP32 on GPIO ports 21,22,23 and 25. A NeoPixel array can be connected to the default GPIO pin 12.
The servo motors and NeoPixels can be controlled by the above MyBlocks. Below we describe each of the MyBlocks.

init_neo_servo

This MyBlock needs to be called once at the start of your program, only if you are using servo’s and/or neopixels. The MyBlock initializes the byte arrays and global variables needed for communicating with the LMS-ESP32.

send_servo_neo(port)

Every time a change needs to be communicated to the LMS-ESP32 with regards to servo’s or neopixels, this function needs to be called. When the port parameter is left empty, the default port will be Port A.  Multiple changes to the neopixels can be accumulated before calling this function.

servo(s1,s2,s3,s4)

This MyBlock sets the values (0-180) for the servo’s S1, S2, S3, and S4 which are connected to GPIO21, 22, 23, and 25, respectively. After calling this MyBlock, the send_servo_neo(port) MyBlock needs to be called.

neopixel_init(num,pin)

Initializes num NeoPixels connected to GPIO Pin pin. By default, an array of 64 neopixels is defined at GPIO12.

neopixel_clear

This MyBlock sets all NeoPixels to the value (0,0,0), effectively switching them off. To effectuate this command, it should be followed by a call to send_servo_neo(port).

neopixel(nr,r,g,b)

This MyBlock sets the values for NeoPixel number nr to  r,g,b. Only after calling the send_servo_neo(port) MyBlock, the new values are passed to the LMS-ESP32.  Multiple neopixels can be set before calling send_servo_neo(port) function. To show the newly set NeoPixels, the function neopixel_show should be called, again followed by a call to send_servo_neo(port).

neopixel_show

This MyBlock lets the LMS-ESP32 show the new values of the NeoPixels. A call to this MyBlock should be followed by a call to send_servo_neo(port).

Debug MyBlocks

In the MINDSTORMS robot inventor app, a special debug mode can be enabled. This also gives access to 4 so-called Debug Blocks. You can read how to enable debug mode on the GitHub page of Maarten Pennings.
We use the following 3 debug Blocks:

The first Blocks reads the n-th raw value of the sensor from the specified mode. Each sensor can have multiple modes. In the BluePad32-LMS firmware, we emulate a single sensor in a single mode.
The second Block allows sensing data – this can be an array of values – to the specified mode M0 of the sensor.
The third Block switches between modes of a sensor. This needs to be called prior to reading or sending values from another mode than the last one used.

Implementation of gamepad MyBlock using debug Blocks

Using the Debug Blocks for reading raw values of a sensor we fill global variables according to the status of the GamePad. Below the MyBlock definition is shown.

Each of the global variables is filled with the value read from mode M0 of the sensor with a mapping of the specific word to the variable as shown in the table above.