GDMS:Pocket

Goblindoid Dungeon Mastering System for microcontroller-based handheld.

Concept:

Dungeon master's companion designed for ease of use and customization. GDMS-pocket is designed to be as ifnoranle as it is helpful - providing that last minute name or encounter when called upon but staying out of the limelight and keeping you engaged with the game.

future ideas

• add a little icon to be displayed for each of the pages
• Add an idicator LED (breath for on status), pop for button pushes.
• Add a beep indicator via passive buzzer (different tones for higher or lower results on tables)

Hardware:

Pin Mapping (Feather RP2040 Adalogger)

OLED Display (SH1107, Software SPI)

OLED Pin	Feather Pin
VCC	3V3
GND	GND
SCL (CLK)	D13
SDA (DATA)	D12
DC	D11
CS	D10
RST	D9

Buttons (Active-Low, Using Internal Pull-Ups)

Button	Feather Pin
Up	A2
Down	A3
A	A1
B	A0

Buzzer (Passive)

Signal	Feather Pin
SIG	D5
VCC	3V3
GND	GND

LED

LED Connection	Feather Pin
Anode (via resistor)	D24
Cathode	GND

Component Information Table

Component ID	Sensor Name	Operational Voltage	Data Type	I²C address	Notes
RP2040 Adalogger		3.3-5			built in SD - See MCU table in logs and documentation
SSD1306	0.96" OLED Display	3.3-5	Digital	0x3C
SH1107	1.5" 128 x 128 OLED display	3.3	Digital	NA - SPI	Modified library default_x_offset
WWZMDiB	SD TF Card Adapter Reader Module	3.3-5		NA - SPI

Possible future components

• TO5100 : charging
• ESP32
• SHARP memory LCD 200 x 400

Wiring:

Buttons

Button	Right Pin	Left Pin
Up	GND	D9
Down	GND	D10
A	GND	D5
B	GND	D6

OLED SSD1306

SSD1306 Pin	Board Pin
GND	GND
VCC	3v3
SCL	A5
SDA	A4

WWZMDiB SD Card reader

SSD1306 Pin SD Card Reader	Board Pin
CS	D5
SCK	D13
MOSI	D11
MISO	D12
VCC	3v3
GND	GND

Software

Language Choice

The native arduino language was chosen for it's low RAM cost for high responsivness.

Functionality Summary for POC:

1. Navigate pages with titles corresponding to folders contained within the root directory.
2. Display the titles of csv files contained within folders as a list on each page.
3. Allow users to select which entry they would like to "Roll" on
4. "Roll" a result by randomly selecting an entry from lists contained within csv files.

Additional Functionality for Future Iterations.

1. When CSV files contain 2 columns, column 1 is used to provide weights to different results. Otherwise entries have equal weights.
2. "About" menu displaying controls and how, why, when, and by whom GDMS was made. User manual available on website.
3. Interpret JSON files containing "recipes" which chain csv files together to create more complex generators.
4. Display the titiles of JSONS along side simple csv files (such as in item 2). Indicator LED "pops" when selectiosn are made.
5. Allow users to save up to 10 generated items to a "Saved" page. Each saved entry is saved to the SD card and thus creates a new entry in a list.
6. Allow users to delete saved entries on the "Saved" page.
7. add a neopixel LED
8. Buzzer beeps when user "rolls"
9. Settings menu allowing users to reduce LED brightness, change LED breathing rate, change pitch and volume of beeps, etc.
10. Indicator LED provides "breathing" UI to indicate power state

Cwazy functionality

1. Random Mode - randomizes your randomization. user hits RANDOM and a random entry appears
2. Ambient Mode - randomly generates entries every 10 seconds for 2 minutes.
3. Music mode. Generative ambient.

important usability features

• long folder names truncated to prevent header wrapping and overwriting content beloe.
• screen scrolling when reading an entry allows for entries longer than 6 rows
• entry file extensions stripped to sabe space and preserve readability

Folder and Data Structure

• Data directory: Folders are all held in a main directory named: "Data"
• Page directory: Each folder's name within the data directory will be used to generate the titles at the top of the pages in the interface. e.g. "names", "dice", "encounters".

Library Table

Relevant Device	Library Names	Include call	Author	Desciption
IIC devices	Wire	<Wire.h>	Arduino ?	used for IIC work
SSD1306 OLED	Adafruit SSD1306	<Adafruit_SSD1306.h>	Adafruit	OLED driver library for small screens
SSD1306 OLED	Adafruit GFX library	<Adafruit_GFX.h>	Adafruit	core graphics library for Adafruit displays
SSD1306 OLED	U8g2		olikraus	SSD1306 screen library with smaller RAM footprint for many sensors
RP2040 Adalogger	SdFat - Adafruit Fork		Adafruit	Enables reading Fat formatted SD cards via Adalogger built in SD card module

AI generated Description

Functional Specification: SD-Based Random Table System (POC)

Overview

The system is a microcontroller-based Dungeon Master aid that reads plain text data from an SD card and displays randomly selected entries on a small screen. All interaction is driven by a simple category-based interface. The system runs on a adafruit RP2040 Adalogger feather. UI is provided by a 0.96" SSD1306 OLED using IIC, 4 buttons, an LED, and passive buzzer.

Data Layout

• The SD card contains a top-level directory named /DATA.
• Inside /DATA, users may create one-level-deep category folders.
  • Folder names define category/page names in the UI.
  • No nested folders beyond this level are supported.
• Each category folder contains .csv files only.
• Each .csv file represents a random table with one entry per line.

Example: /DATA /NPC names.csv flaws.csv /DICE d20.csv d100.csv

Startup / Discovery

• On boot (or user-triggered rescan), the system:
  1. Enumerates all immediate subfolders of /DATA.
  2. Stores their names as available Categories.
• No recursive directory traversal is performed beyond this level.

UI Behavior

• Each Category corresponds to one folder under /DATA.
• When a Category is selected:
  • The system lists all .txt files in that folder.
• The user scrolls and selects a file.
• Upon selection:
  • The system reads the file and displays one randomly selected line.