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Nie, dziękuję Przekieruj mnie tamhow use i2c lcd to openbeken
• Assign two free GPIOs of your OpenBeken device the roles “I2C_SDA” and “I2C_SCL”.
• Wire the I²C LCD module (PCF8574 backpack + HD44780 display) to VCC, GND, SDA, SCL.
• Reboot, run i2c_scan from the OpenBeken console or Web-UI to learn the LCD’s address (usually 0x27 or 0x3F).
• Register the display with the built-in driver
addI2CDevice_LCD_PCF8574 <hex-address>
• Use the LCD commands (lcd_clear, lcd_setCursor x y, lcd_print "text", …) or automation rules to send text.
Key points
• No additional libraries or flashing are required – support is already in current OpenBeken nightlies (v1.16.x, 2024-03 and newer).
• The driver assumes a standard 16×2/20×4 HD44780; contrast/back-light are controlled by PCF8574 pins.
• If nothing is shown, check address jumpers, pull-ups and 3 V logic levels.
Hardware layer
• I²C LCD modules embed a PCF8574 (or PCF8574A) 8-bit I/O expander which drives the HD44780 bus in 4-bit mode.
• Operating voltage: most modules tolerate 3.3 V. If yours is 5 V-only, add a logic-level MOSFET or use a 5 V-tolerant BK7231N pin pair (consult datasheet).
• Typical pinout
– GND → BK GND
– VCC → 3.3 V (or 5 V*)
– SDA → GPIO-set-as-I2C_SDA
– SCL → GPIO-set-as-I2C_SCL
– A0–A2 → address select (leave high for 0x27 / 0x3F).
Firmware configuration (OpenBeken ≥ 1.16.x)
a. Pin roles
– Web > Config > “Pins” → assign “I2C_SDA” to e.g. GPIO6, “I2C_SCL” to GPIO7 (pins differ per board).
– Save & reboot (pull-ups inside BK7231 are enabled automatically).
b. Verify bus
– Console: i2c_scan → returns all found addresses.
c. Attach the driver
– addI2CDevice_LCD_PCF8574 0x27 (replace with address).
– Driver is stored in flash and initialises after every reboot.
d. Basic commands (suffixes are case-insensitive):
• lcd_print "Hello" – prints at current cursor position.
• lcd_setCursor col row – zero-based.
• lcd_clear, lcd_home, lcd_backlight 0/1.
• lcd_printLong <number> – convenience for integer values.
e. Rule integration example
rule1
on Power1#State do
lcd_setCursor 0 0; lcd_print "Relay:"; lcd_printLong %value%
endon
rule1 1The LCD is now updated every time Power1 changes.
Electrical considerations
• Pull-ups: Module usually has 4.7 kΩ resistors on SDA/SCL; disable any on the BK board if duplicates drop below 1.5 kΩ (risk of bus contention).
• Back-light pin (P3 on PCF8574) is active-low on many backpacks; OpenBeken treats “1” as back-light ON, invert logic with lcd_backlight_invert 1 if required.
• Contrast pot: adjust until faint rectangles disappear after power-up.
Typical failure modes
• “All blocks lit” → wrong initialisation → wrong address or wiring.
• Garbled characters after a while → bus speed too high; limit with i2c_setClock 40000.
• Nothing found by i2c_scan → mis-assigned pins or pull-ups missing.
• Driver status (May 2024): merged in commit fe0f5d9; supports 16×1, 16×2, 20×2, 20×4; custom characters and bar-graph API are on the roadmap.
• Web UI is gaining a live widget; nightly builds already allow remote text entry without console.
• Community is adding UTF-8 translation tables (limited by HD44780 ROM variants).
PCF8574 address calculation
0b0100 011 PCF8574 base 0x20
ABC A2 A1 A0 jumpersIf A2=A1=A0=1 → 0x27.
For PCF8574A the base is 0x38 (0x3F all high).
Timing
HD44780 needs >37 µs for most commands. The driver keeps an internal millis() timer to respect that; avoid calling LCD functions inside tight loops without delay.
• OpenBeken and the LCD driver are under the Apache-2.0 licence—respect attribution when distributing binaries.
• Ensure you do not display misleading data in safety-critical products (e.g. energy meters).
• If the device is mains-powered, follow IEC 62368 isolation rules when mounting the display and avoid user-accessible conductive parts.
Implementation checklist
□ Pick two unused GPIOs (check that they are not needed for relays/LEDs).
□ Enable I²C roles, reboot, run i2c_scan.
□ Register LCD, test with lcd_print.
□ Write rules or MQTT templates to push data.
Best practices
• Keep I²C wires <20 cm.
• Use shielded cable if running parallel to mains traces.
• If multiple I²C devices share the bus, standardise on 100 kHz; some sensors (e.g. BH1750) misbehave at 400 kHz.
Potential challenges & mitigation
• “Ghosting” characters on long cables → lower clock, twist SDA/SCL with GND.
• Different PCB layouts invert BL pin → use lcd_backlight_invert.
• The present driver does not yet support display scrolling or CGRAM upload from rules; compile a custom build with USE_LCD_CUSTOM_CHARS if required.
• UTF-8 beyond ASCII is only partially supported due to ROM variant mismatches (Japanese vs. European char-sets).
• Investigate OpenBeken’s upcoming “Dashboard widgets” to bind LCD output directly to MQTT topics.
• Explore chaining multiple PCF8574 devices (change address pins) to drive buttons or LEDs in the same enclosure.
• Consider higher-resolution OLEDs (SSD1306, SH1106) – drivers exist and use the same I²C pins.
Useful resources
• Official wiki topic “I2C devices – LCD” (github.com/openshwprojects/OpenBK7231T_App/wiki)
• Forum thread “LCD driver PR #1227” for bleeding-edge patches
• NXP PCF8574 datasheet (Rev 10, Feb 2023)
Connecting an I²C LCD to OpenBeken is a four-step process: set two GPIOs to I²C roles, wire SDA/SCL + power, scan for the address, then register the module with addI2CDevice_LCD_PCF8574. Once attached, you can control the display from the console, MQTT, or automation rules. Current firmware (2024) supports the common 16×2/20×4 HD44780 displays, including back-light control, cursor positioning and numeric/ASCII printing, making it a straightforward way to add local visual feedback to any BK7231-based smart device.