How to Connect I2C LCD (PCF8574 + HD44780) to OpenBeken BK7231 – Wiring, Address, Commands

User question

how use i2c lcd to openbeken

Artificial Intelligence Response

Direct answer to the question

• Wire the I2C LCD (PCF8574 backpack + HD44780 display) to your OpenBeken device, assign two pins as I2C_SDA and I2C_SCL in the web UI, then reboot.
• In the OpenBeken console, run i2c_scan to find the LCD’s address (commonly 0x27 or 0x3F).
• Register the display: addI2CDevice_LCD_PCF8574
• Use lcd_clear, lcd_setCursor , and lcd_print "text" to control the display. Put the commands in autoexec.bat to make them persistent. (elektroda.com)

Key points

• Works out of the box in current OpenBeken builds; no extra libraries are needed. (elektroda.com)
• Typical addresses for PCF8574/PCF8574A modules are 0x20–0x27 and 0x38–0x3F; 0x27/0x3F are most common defaults. (github.com)

Detailed problem analysis

1) Hardware and electrical layer

• The I2C “LCD modules” are standard HD44780 character displays driven over I2C by a PCF8574 8‑bit expander in 4‑bit mode. The backpack routes expander pins to RS, E, D4–D7, plus backlight and contrast.
• Addressing: PCF8574 (base 0x20) and PCF8574A (base 0x38) set their I2C address via A0–A2 jumpers; unmodified boards are typically 0x27 or 0x3F. (github.com)
• Voltage: many boards tolerate 3.3 V operation; some are happier at 5 V. If powering the LCD at 5 V, ensure the I2C pull‑ups on the backpack are not pulling SDA/SCL to 5 V into a 3.3 V MCU; use a level shifter if in doubt.
• I2C wiring: keep SDA/SCL short (<20–30 cm), twisted with ground if longer, and rely on the backpack’s 4.7 kΩ pull‑ups (most include them). (doc.grablo.co)

2) OpenBeken configuration (web UI → Config → Pins)

• Assign one free GPIO as I2C_SDA and another as I2C_SCL, save, and reboot.
• Open Console and verify the bus: i2c_scan. Note the LCD address found.
• Attach the LCD driver/device: addI2CDevice_LCD_PCF8574
• Basic runtime control:
  • lcd_clear
  • lcd_setCursor (zero‑based)
  • lcd_print "Hello"
  • lcd_backlight 1 (or 0 to turn off)
    These commands mirror the common character‑LCD functions and are available directly in the console, rules, or via MQTT. (elektroda.com)

3) Persisting the setup (autoexec)

• Config → Startup Command (autoexec.bat), for example:
  • addI2CDevice_LCD_PCF8574 0x27
  • lcd_clear
  • lcd_setCursor 0 0
  • lcd_print "OpenBeken Ready"
    This ensures the LCD initializes at every boot. (elektroda.com)

4) Troubleshooting and signal integrity

• Nothing detected by i2c_scan: swap SDA/SCL if miswired, confirm grounds, and check that the module is powered. Ensure the I2C address jumpers are not shorting to an unintended address. (elektroda.com)
• Blank line of “blocks” or no characters: adjust the contrast potentiometer on the backpack.
• Intermittent or garbled text: shorten the cable, check for adequate pull‑ups, and avoid running I2C alongside mains conductors. (doc.grablo.co)

5) Printing live data (example rule)

• A minimal rule that updates when a relay changes:
  • rule1
  • on Power1#State do lcd_setCursor 0 0; lcd_print "Relay:"; lcd_printLong %value% endon
  • rule1 1
    This shows how to bind system events to LCD updates. (elektroda.com)

6) Legacy/alternative initialization (if your build is older)

• Some older builds used startDriver LCD_PCF8574 followed by LCD_Clear/LCD_Print. If addI2CDevice_LCD_PCF8574 is not recognized, update to a current release or use the legacy startDriver path. Current stable/nightly releases retain PCF8574 LCD support. (github.com)

Current information and trends

• As of January 27, 2026, OpenBeken releases are in the 1.18.x line and include PCF8574‑LCD support among I2C devices. (github.com)
• Typical user workflows rely on addI2CDevice_LCDPCF8574 plus lcd* commands; this replaces ad‑hoc Arduino libraries since the firmware exposes native commands and MQTT/rules integration. (elektroda.com)
• Trend note: many projects are moving to I2C OLEDs (SSD1306/SH1106) for richer UIs, but the PCF8574+HD44780 remains attractive for low‑cost, daylight‑readable status. (General industry observation; for address ranges and common alternatives see community/device docs.) (tasmota.github.io)

Supporting explanations and details

• Address math: PCF8574 addresses are 0x20–0x27; PCF8574A are 0x38–0x3F. Solder pads A0/A1/A2 pull the three LSBs to 0 or 1; all high commonly yields 0x27 (or 0x3F for ’A’). (github.com)
• Backlight control: many backpacks wire backlight as active‑low; the lcd_backlight command abstracts this, so use lcd_backlight 1/0 rather than toggling pins. (Behavior consistent with common PCF8574 LCD stacks.) (elektroda.com)
• I2C pull‑ups: multiple modules on one bus can reduce effective pull‑up resistance; if SCL/SDA rise times look slow or bus looks “stuck,” remove duplicate pull‑ups or add series resistance per best practice. (doc.grablo.co)

Ethical and legal aspects

• Safety around mains: many OpenBeken devices are line‑powered. Maintain basic insulation distances, route low‑voltage I2C cabling away from HV sections, and enclose the display so no user can touch mains‑referenced conductors. Comply with local low‑voltage and household appliance safety norms (e.g., IEC 62368‑1).
• EMC: long unshielded I2C leads inside mains devices can couple noise; mitigate with short runs, twisted pairs, and proper grounding.

Practical guidelines

• Implementation checklist
  • Assign I2C_SDA/I2C_SCL roles; wire VCC/GND/SDA/SCL; reboot.
  • i2c_scan → note address.
  • addI2CDevice_LCD_PCF8574 .
  • lcd_clear; lcd_setCursor 0 0; lcd_print "OK". (elektroda.com)
• Best practices
  • Keep I2C ≤20–30 cm; if you must go longer, slow the bus and twist with GND.
  • Use 3.3 V LCDs when possible; if using 5 V boards, ensure SDA/SCL do not exceed 3.3 V at the MCU.
• Potential challenges and mitigations
  • “No device found” → swap SDA/SCL, check grounds, verify address jumpers.
  • “Blocks only” → adjust contrast, then verify commands. (elektroda.com)

Possible disclaimers or additional notes

• Character set/UTF‑8: HD44780 ROM variants differ; extended characters may render inconsistently without custom glyphs.
• Older firmware builds may use a different command naming scheme; if addI2CDevice_* is missing, upgrade to ≥1.16 or use legacy startDriver LCD_PCF8574. (github.com)

Suggestions for further research

• Review OpenBeken’s “Console Commands” and I2C device notes in the project docs/wiki for any build‑specific LCD options. Also check the current release notes (1.18.x) before deploying. (github.com)
• If you outgrow character LCDs, explore the SSD1306/SH1106 OpenBeken drivers; pin reuse is straightforward. (tasmota.github.io)

Brief summary

• Configure I2C pins, wire the module, scan for its address, register it with addI2CDevice_LCDPCF8574, and print using lcd* commands. Persist the steps in autoexec.bat. Current OpenBeken (1.18.x, Jan 2026) has native support, so no extra libraries are required. (elektroda.com)

If you share your board model (e.g., BK7231T/N module type) and LCD size (16×2 or 20×4), I can give you an exact pin map and a ready‑to‑paste autoexec.bat.

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.