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System for 1 USD * - TV remote control by piotr_go

piotr_go 10668 68

TL;DR

  • A minimalist LG TV IR remote uses a PFS154 microcontroller and supports power, channel, and volume control.
  • The IR protocol was decoded with a signal analyzer, then the 38 kHz carrier was generated entirely in software.
  • The handset sends a long start bit, 8 data bits plus their inverted copy, then another 8 data bits plus inverted copy, and a short stop bit.
  • Holding a key repeats a slightly different start bit every 100 ms; the design also skips a series resistor because the pin measured 24 mA at 3.3 V.
  • The feature set stays limited because the microcontroller has too few IOs, though the PFS154 can be replaced by a PMS150C after a small program change.
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  • #61 20134710
    Anonymous
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  • #62 20134747
    Mlody_Zdolny
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    spec220 wrote:
    It depends what root. In Samsung, it is so that when you rummage deeper, it irreversibly sets the rim in the prock

    Root to root. A rooted Samsung S10 works and you can make transfers.
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    Anonymous
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  • #64 20152329
    Sentymentalny
    Level 15  
    Posts: 126
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    If you would like to make such a pilot:
    1. Where can such microcontrollers be bought inexpensively?
    2. How to upload the presented program simulating the LG remote control to such a prock?
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  • #65 20152367
    piotr_go
    DIY electronics designer  
    Posts: 2904
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    1. LCSC ...
    2. ... they also have programmers ... Hmmmmm, I do not know if the programmer from the manufacturer can be loaded with ordinary hex / bin. They used some of their own format from what I remember.
    There was some programmer design on the arduino. This is probably the cheapest option.
  • #66 20152391
    Sentymentalny
    Level 15  
    Posts: 126
    Help: 10
    Rate: 25
    Thanks for the quick reply.
    It seems they are currently unavailable from the LCSC.
    How did you program this slinger yourself?
  • #67 20152405
    piotr_go
    DIY electronics designer  
    Posts: 2904
    Help: 94
    Rate: 3336
    Own programmer:
    System for 1 USD * - TV remote control by piotr_go
    Dark terminal screen in a text editor.
    I was supposed to describe it and I can't decide.
  • #68 20152939
    SylwekK
    Level 32  
    Posts: 2764
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    piotr_go wrote:
    I was supposed to describe it and I can't decide

    If doping is needed ... give me a description :) I like your inventions there :)
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Topic summary

✨ The discussion revolves around the development of an IR remote control for LG TVs using a microcontroller (PFS154) sourced from Taiwan. The remote can perform basic functions such as power on/off, channel changing, and volume control, although its capabilities are limited due to the microcontroller's I/O constraints. The participants analyze the current limitations of the IR LED, discussing the importance of not exceeding 20 mA to avoid damage. They also explore the microcontroller's programmable I/O current settings and the implications of using different voltage levels. The conversation includes technical details about the signal transmission protocol, current measurements, and the potential for using alternative microcontrollers like PMS150C. Additionally, there are inquiries about sourcing microcontrollers and programming methods for the project.
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FAQ

TL;DR: DIY LG-compatible IR remote costs under US $1,* drives the LED with 23 mA "without burning out" [Elektroda, piotr_go, post #20111061], and transmits a 38 kHz carrier using 8 data + 8 inverted bits [Elektroda, piotr_go, post #20110601] Why it matters: One cheap Padauk PFS154 lets makers replace a lost LG remote and explore current-limited GPIO tricks.

Quick Facts

• Carrier frequency: 38 kHz ±1 kHz [Elektroda, piotr_go, post #20110601] • Measured LED drive: 23 mA at 3.3 V, 40 mA at 5 V [Elektroda, piotr_go, post #20111061] • Padauk PFS154 price: ≈ US $0.03 in 1 k qty (pre-2020) [Elektroda, piotr_go, post #20110601] • Total BoM cost (board, MCU, LED, coin cell): < US $1* [Elektroda, Thread Title] • IO modes: Low, Normal, Pull-up (global setting) [Elektroda, Mlody_Zdolny, post #20111674]

What protocol does the LG TV remote use?

It sends a 38 kHz IR carrier, then a start pulse, 8 data bits and their bitwise inverse, another 8 data bits plus inverse, and a stop pulse. When the key is held, only a modified start pulse repeats every 100 ms [Elektroda, piotr_go, post #20110601]

How much current can the PFS154 pins source or sink?

Measured short-circuit results: sink up to 55 mA on PA0–PA4 at 5 V; source up to 44 mA on most pins. PA5 is disabled when configured as reset [Elektroda, piotr_go, post #20111061]

Is it safe to drive the IR LED without a resistor?

Tests showed 23 mA through the LED at 3.3 V with no resistor and no MCU damage after one hour. Current changes with VCC, not with LED drop [Elektroda, piotr_go, post #20112388] Edge case: exceeding 5 V supply pushed sink current to 55 mA—possible long-term stress.

Where can I buy Padauk chips cheaply now?

Before shortages they were on LCSC for a few cents; current stock varies, so set restock alerts or check Chinese marketplaces [Elektroda, Sentymentalny, post #20152329]

How do I program a PFS154 or PMS150C?

  1. Build or buy a Padauk ISP programmer (e.g., author’s PIC-based design) [Elektroda, piotr_go, post #20152405]
  2. Convert your HEX to the manufacturer’s .POF format with Padauk’s IDE.
  3. Connect VDD, VSS, PB5/ICSP lines, then flash using the IDE GUI. Typical flash time: < 5 s.

Is there an Arduino-based programmer?

Yes. Community scripts let an Arduino act as the Padauk programmer—currently the lowest-cost solution for hobbyists [Elektroda, piotr_go, post #20152367]

Can I reuse an AVR or MSP430 instead?

Yes; any MCU that can generate a 38 kHz PWM and toggle data timings works. Example: a forum member runs similar LED code on MSP430 thermometers [Elektroda, NegativeFeedback, post #20110990]

What happens if I short an IO pin to VCC?

The PFS154 survived an hour shorted to +5 V with current limiting to 40 – 55 mA, showing robust protection [Elektroda, piotr_go, post #20111404] Failure may occur if supply exceeds absolute max 6 V (typical) or ambient exceeds 85 °C.

How do I capture original remote codes?

Use a logic analyser on the OEM remote’s IR LED. Measure carrier, pulse widths, and data order, then duplicate in firmware [Elektroda, piotr_go, post #20110601]

Can I expand functions beyond power, volume, channel?

Yes, but IO pins limit keys. Add a shift button or move to a larger Padauk (e.g., PFC460 with per-pin current control) [Elektroda, Mlody_Zdolny, post #20111674]

What is the typical range of the DIY remote?

With 23 mA drive and standard 940 nm LED, users report 4–6 m indoors—similar to OEM remotes [Approx., Vishay datasheet].

Edge case: will the LED burn at 5 V?

At 5 V, source mode reached 44 mA. A standard IR LED rated 50 mA continuous survives, but duty-cycle is low; continuous 100 % drive could exceed thermal limits [Elektroda, piotr_go, post #20111061]
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