E-Paper meeting room dashboard firmware for the LaskaKit ESPink board with a Good Display GDEY075T7 7.5" 800×480 BW display.

Shows the room's daily schedule (fetched directly from Microsoft 365 Graph API), current time indicator, temperature/humidity (SHT40 sensor), and battery level. Refreshes every 5 minutes using deep sleep.

src/
├── config.h          – All configurable parameters (WiFi, Azure, pins, etc.)
├── main.cpp          – Setup-only loop: power on → read sensors → fetch calendar → draw → deep sleep
├── ms_graph.h/cpp    – OAuth2 client-credentials flow + MS Graph calendarView API
├── display_ui.h/cpp  – Full-screen e-Paper rendering (portrait 480×800 layout)

1. Power on peripherals (GPIO drives MOSFET gate for display + I2C bus)
2. Read battery voltage via ADC + voltage divider
3. Read SHT40 temperature & humidity over I2C
4. Connect to WiFi
5. Sync time via NTP (pool.ntp.org)
6. Acquire OAuth2 access token from Azure Entra ID
7. Fetch today's calendar events from MS Graph (/users/{room}/calendarView)
8. Disconnect WiFi
9. Render dashboard on e-Paper display
10. Enter deep sleep for 5 minutes

# Install Homebrew (if not already installed)
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

# Install Python 3 and PlatformIO CLI
brew install python3
pip3 install platformio

# Install USB-to-serial driver (CH340) if not auto-detected
# Most modern macOS versions include the driver. If not:
brew install --cask wch-ch34x-usb-serial-driver

1. Python 3 — Download and install from python.org. Check "Add Python to PATH" during install.
2. PlatformIO CLI:

   pip install platformio

3. USB driver — Install the CH340 driver (ESPink uses CH340 USB-to-serial chip).
4. Plug in the board and note the COM port in Device Manager (e.g., COM3).

sudo apt update && sudo apt install python3 python3-pip
pip3 install platformio

# Add your user to the dialout group for serial port access
sudo usermod -a -G dialout $USER
# Log out and back in for the group change to take effect

# The CH340 driver is included in the kernel. Verify with:
ls /dev/ttyUSB*

pio --version
# Should print something like: PlatformIO Core, version 6.x.x

Follow these steps for each new meeting room display you deploy.

If you already have an app registration, skip to the per-room steps.

1. Go to Azure Portal → Entra ID → App registrations
2. Click New registration
   • Name: Meeting Room Display
   • Supported account types: Single tenant
   • Redirect URI: leave blank
3. Go to Certificates & secrets → New client secret
   • Copy the Value (this is AZURE_CLIENT_SECRET). It is only shown once!
4. Note down from the Overview page:
   • Application (client) ID → AZURE_CLIENT_ID
   • Directory (tenant) ID → AZURE_TENANT_ID

Each meeting room in Microsoft 365 has a room resource mailbox. Ask your Exchange/M365 admin for the room's email address, e.g., meeting-room-lobby@yourcompany.com.

1. Get the correct Service Principal Object ID

Connect-MgGraph -Scopes "Application.Read.All"
$sp = Get-MgServicePrincipal -Filter "appId eq 'AZURE_CLIENT_ID'"
$sp.Id

2. Connect to Exchange Online PowerShell

Install-Module ExchangeOnlineManagement -Scope CurrentUser -Force
Connect-ExchangeOnline

3. Define variables

$AppId = "xxx"
$SpObjectId = "<PASTE_ENTERPRISE_APP_SERVICE_PRINCIPAL_OBJECT_ID_HERE>"
$AdminUnitId = "xxx"

4. Create the Exchange “pointer” to the Entra service principal

New-ServicePrincipal -AppId $AppId -ObjectId $SpObjectId -DisplayName "ADD NAME HERE"

5. Assign the scoped role Application Calendars.Read to the AU

New-ManagementRoleAssignment -Name "ADD NAME HERE" `
  -App $SpObjectId `
  -Role "Application Calendars.Read" `
  -RecipientAdministrativeUnitScope $AdminUnitId

6. Test Scope

Test-ServicePrincipalAuthorization -Identity $SpObjectId -Resource "meeting-room-half-life@noibit.com"

By default, Exchange replaces the meeting subject with the organizer's name for room mailboxes. To show actual meeting titles, an Exchange admin should run:

# Connect to Exchange Online
Connect-ExchangeOnline

# Check current settings
Get-CalendarProcessing -Identity "room-email@yourcompany.com" | FL DeleteSubject, AddOrganizerToSubject

# Fix it
Set-CalendarProcessing -Identity "room-email@yourcompany.com" -DeleteSubject $false -AddOrganizerToSubject $false

Note: The firmware handles the duplicate gracefully — if subject equals organizer name, it shows the name only once. But running the PowerShell fix above will show actual meeting titles.

Edit src/config.h:

// WiFi credentials for the room's network
#define WIFI_SSID           "YourWiFiSSID"
#define WIFI_PASSWORD       "YourWiFiPassword"

// Azure credentials (from step 1)
#define AZURE_TENANT_ID     "your-tenant-id"
#define AZURE_CLIENT_ID     "your-client-id"
#define AZURE_CLIENT_SECRET "your-client-secret"

// This room's mailbox
#define ROOM_EMAIL          "room-email@yourcompany.com"
#define ROOM_DISPLAY_NAME   "Room Name"

Other settings you may want to adjust:

cd meeting-room-display

# For ESPink v2.7 (ESP32):
pio run -e espink-v2 -t upload

# For ESPink v3.5 (ESP32-S3):
pio run -e espink-v3 -t upload

If auto-detection fails, specify the port explicitly:

# macOS
pio run -e espink-v2 -t upload --upload-port /dev/cu.usbserial-XXXX

# Linux
pio run -e espink-v2 -t upload --upload-port /dev/ttyUSB0

# Windows
pio run -e espink-v2 -t upload --upload-port COM3

pio device monitor -e espink-v2

You should see output like:

====== Meeting Room Display ======
[PWR]  peripherals ON
[BAT]  4.12 V  (93%)
[SHT40] 23.1 °C   45 %RH
[WiFi] connecting to YourSSID . OK  IP=10.0.0.42  RSSI=-45 dBm
[NTP]  syncing  OK
[NTP]  2026-02-27 09:15:22 CET
[Graph] token obtained (1942 chars)
[Graph] fetched 5 calendar events
[WiFi] disconnected
[PWR]  peripherals OFF
[SLEEP] deep sleep for 5 min

All dependencies are managed by PlatformIO and downloaded automatically on first build.

The board uses deep sleep between refreshes. Approximate power draw:

With a 5000 mAh battery and 5-minute refresh interval, expect several months of battery life.

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