Ready to deploy design #8

Read this document from start to end before building anything. Ensure you understand everything.

This setup has not been tested at the system level. If you try, please, let me know.

Hardware features

• USB connectivity
• Power through USB cable
• Relative rotary encoders (with push button): x4
• Up to 21 additional push buttons

Needed parts

Common:

Item	Quantity	Notes
Bare bone rotary encoder	4	With built-in push button
Push buttons	up to 21	General purpose inputs (up to you)
PISO shift register	3	74HC165N (mandatory)
Resistors	25	Any impedance in the range from 1K-ohms to 10K-ohms
Standard perfboard sized 24x10 holes	1	Single-sided or double-sided
LilyGO T-QT PRO DevKit board	1	With male pins already soldered
Pin header (male or female up to you)	37	For external wiring
External Antenna with proper connector	1	Optional
USB type C cable	1

Other parts (quantity unknown):

• Wire with Dupond terminals (for external wiring). A kit for protoboards will do the job. ¿Male or female? the opposite to pin headers. Sacrifice some of them for other wiring.
• Welding tin.

Other notes:

• The packaging of the shift registers will show a small circle next to pin #1, which is tagged as ~LD here.
• T-QT's builtin push buttons will also work as input numbers 60 and 61. There is little use for them, except for testing.

Pin-out plan for the T-QT DevKit board

GPIO	Input	Output	Usage	Notes
34	OK	OK	NEXT
33	OK	OK	LOAD
39	OK	OK	SERIAL
38	OK	OK	ROT1_A	outputs PWM signal at boot
37	OK	OK	ROT1_B	outputs PWM signal at boot
36	OK	OK	ROT2_A
35	OK	OK	ROT2_B
48	OK	OK	ROT3_A
18	OK	OK	ROT3_B
17	OK	OK	ROT4_A	outputs PWM signal at boot
16	OK	OK	ROT4_B

Circuit layout

We are reusing the shift registers example from the switches subsystem as a satellite circuit:

External wiring goes as follows:

This layout includes the following subsystems (read for an in-depth explanation):

• Power through an external power source (USB cable).
• Switches through shift registers.
• Relative rotary encoder bare bone type.

Notes and build tips:

• Some components may look very small, not matching their actual size. This is not a mistake. They must be placed in vertical position, s o they lie in a minimal surface of the perfboard.

External wiring

• Each input has an assigned number in the circuit layout. Certain inputs have a particular function, so attach them properly.
• Push buttons:
  • There are several COM pins. You may use any of them.
  • Wire COM to just one terminal of each push button in a chain.
  • Wire the other terminal of each push button to one of the light-blue pins.
  • Bare bone rotary encoders: their built-in push button must be wired like any other push button, being SW and SW COM the involved terminals.

Firmware upload

At Arduino IDE, configure the board manager as this:

• Board: "ESP32S3Dev".
• USB CDC on boot: "Disabled".
• USB-Mode: "USB-OTG (TinyUSB)".

1. Plug the USB cable to the DevKit board and upload the sketch with Arduino IDE. If required, in order to enter "boot mode" click the reset button while holding "IO0".
2. Reset.
3. Check that a new USB device is recognized at the host computer, named "ButtonBox-8".