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https://github.com/spezifisch/t12pensolder

A better firmware for "Pen Solder V3" soldering irons with USB-C using Hakko T12 tips
https://github.com/spezifisch/t12pensolder

platformio soldering-iron ssd1306 stm32 t12

Last synced: 3 months ago
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A better firmware for "Pen Solder V3" soldering irons with USB-C using Hakko T12 tips

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README 

        
# Pen Solder V3 (PSV3) replacement firmware



Cheap soldering iron reverse engineering and replacement firmware.



See also the [write-up on my blog](https://spezifisch.codeberg.page/tags/soldering-iron/).



**Note** that while the product is advertised as a *T12 soldering iron* this is just the name of its ubiquitous soldering tip (*Hakko T12*).

So I needed a more specific name for it and chose the label on its PCB: Pen Solder V3 or short: PSV3.



## Replacement Firmware



Development WIP in [./firmware](./firmware).



![](./fwdisplay.jpg)



Current state (quite usable!):



* soldering tip temperature PID controller code works (adapted from [IronOS](https://github.com/Ralim/IronOS))

* temperature measurement synced with off time of tip switching PWM

* all buttons work

* voltage measurement of soldering tip temperature and VBUS (from USB-PD) work

* display output works (it's connected to non-hardware-I2C pins, so we're bitbanging with [U8g2](https://github.com/olikraus/u8g2) with custom STM32 optimizations for around 170kHz I2C clock speed)

* standby after 60s without activity (partly implemented, just turns tip off at the moment)

* no cold junction compensation (not available on this board)

* no settings storage

* resource usage: around 30/32kB flash, 1.4/4kB RAM (we're splurging a bit by including an additional font and Arduino libs)

* supported boards: V3, V7



## "Pen Solder V3" Description



Its name is: *Portable T12 Electric Soldering Iron PD 65W DC 72W*.



![](./ali_product.jpg)



Tracing the board layout:



![](./layout.jpg)



Which leads to this [Reverse Engineered Schematic](./pen_solder_v3.pdf) (click for PDF):



[![](pen_solder_v3_sch_preview.png)](./pen_solder_v3.pdf)



## "Pen Solder V7"



To compile for V7 boards open `./firmware/platformio.ini` and change the following line:



```ini

-D PENSOLDER_V=3

```



to



```ini

-D PENSOLDER_V=7

```



Thanks to @Gobracket for finding the needed change in the display's setup!



## Flashing



Some test pads are labeled on the board: VSS, CLK, DAT, VDD:



![](./swd.jpg)



Connect them to GND, SWCLK, and SWDIO from your STLink adapter respectively. Do not connect VDD. It's cleaner to supply the board in a more stable manner using an USB-C supply instead.



You can then build and flash my firmware from within VSCode using [PlatformIO](https://docs.platformio.org/en/latest/platforms/ststm32.html) (just press Build/Upload).



### Dumping Stock Firmware



Before flashing a custom image you should backup the stock firmware!



I used the Debian 12 package of [st-tools](https://github.com/stlink-org/stlink) for this:



```

st-flash --hot-plug read t12-f0.bin 0x8000000 32768

```



## Hardware Details



Label on case: T12



PCB:



```

PEN-SOLDER V3 2023-02-02

```



MCU: CHIPSEA F030F6P6

* https://www.st.com/resource/en/datasheet/stm32f030f4.pdf

* https://www.st.com/resource/en/reference_manual/rm0360-stm32f030x4x6x8xc-and-stm32f070x6xb-advanced-armbased-32bit-mcus-stmicroelectronics.pdf



```console

$ st-info --probe 

Found 1 stlink programmers

  version:    V2J34S7

  serial:     ...

  flash:      32768 (pagesize: 1024)

  sram:       8192

  chipid:     0x0440

  descr:      F0xx

```



Big P-MOSFET: NCE30P30K

* https://datasheet.lcsc.com/szlcsc/NCE30P30K_C130106.pdf



Small N-MOSFET driver: 72K

* Maybe: https://pdf1.alldatasheet.net/datasheet-pdf/view-marking/1085166/RUICHIPS/2N7002K.html



OpAmp: 8331CGn04

* https://datasheet.lcsc.com/lcsc/2206101816_Gainsil-GS8331-TR_C157712.pdf



Zener: W3

* Maybe: BZT52C3V3 https://pdf1.alldatasheet.net/datasheet-pdf/view-marking/58974/DIODES/BZT52C3V3.html



SMPS: XL1509-3.3E1

* https://www.xlsemi.com/datasheet/XL1509-EN.pdf



USB: CH224K

* https://datasheet.lcsc.com/lcsc/2204251615_WCH-Jiangsu-Qin-Heng-CH224K_C970725.pdf

* https://www.laskakit.cz/user/related_files/ch224ds1.pdf

* https://components101.com/ics/ch224k-usb-power-delivery-controller-ic



## "STM"32F030 Pinout



* 1: BOOT0 -> 10k to GND

* 4: NRST -> filtered VDD

* 6: PA0 -> not connected here, but optionally a non-populated part could connect it to some kind of SMD part (white square with 4 pads)

* 7: PA1 -> ADC: VIN measurement of 1/11*VBUS

* 8: PA2 -> ADC: Temperature measurement of soldering tip's thermocouple (through amplifier)

* 9: PA3 -> Heating enable for soldering tip

* 10: PA4 -> Button "Minus (-)", high active (10k pull-down to GND, button pulls to VDD)

* 11: PA5 -> Button "Plus (+)", high active

* 12: PA6 -> I2C SCL to display (4k7 to VDD)

* 13: PA7 -> I2C SDA to display (4k7 to VDD)

* 14: PB1 -> Button "Set", high active

* 17: PA9 -> looks like it's not connected to anything, used in stock firmware for display reset

* 19: PA13/SWDIO -> SWD header/pads

* 20: PA14/SWCLK -> SWD header/pads



## CH224K USB-PD Control



CFG1,2,3 pins are not connected to anything. Floating CFG1 means it will request VBUS=20V from USB power supply.

That's a bit concerning given that this means the P-MOSFET gets U_GS=20V (or more) and that's already its U_GSmax.



Too bad those pins aren't connected to the uC or we could switch to a lower USB voltage.



## OpAmp



* Used as non-inverting amplifier, 221x gain

* Input connected to T12 soldering tip pin A (the last ring), (tip pin B (the ring between A and Earth) is connected to GND)

* Zener diode clamps input to 3.3V max.

* Input range should be 14.9 mV max. assuming the output is 3.3V max.