GT Power B6 mini status

[diggit]

This issue is tracking GT Power B6 mini reverse engineering and possibly future suport.

TODOs

• [ ] MCU pinout reverse engineering: 30 % (bit painful on such dense PCB and charger design diverting from what we already know)
• [ ] Guess what driver LCD driver is LCD using
• Implement drivers:
  • [ ] LCD (incl soft SPI) - help is welcome, have look into LCD signal captures and try to find matching LCD(driver) chip.
  • [ ] ADC
  • [ ] PWM (with dithering using DMA)
  • [ ] FLASH writing

Basic info about charger:

• input voltage: 12-26 Vdc
• max charging power: 300 W
• max discharging power: 4 W
• charging current: 0.1-12.0 A
• discharging current: 0.1-3.0 A
• max balancing current: Max 1 A/cell
• NiCd/NiMH cells: 1-16
• Lixx cells : 1-6
• Lead battery: 2V - 20V
• Net weight: 95g
• Dimensions: 87.5 x 48.5 x 30mm

Findings

• at least 4 layer PCB
• TD1509 buck converter (150 kHz, 5 Vout)
• small 3V3 LDO for MCU (5 V -> 3.3 V)
• SDB628 boost converter (1 MHz, 5 V ->12 V)
• AOZ3401 balancer Pmos switches
• GD32F150R8T6 MCU (Cortex M3, 72 MHz, 64 kB FLASH, 8 kB RAM, ) pinout matches STM32F103R8T6 except 2 power pins, which are replaced by port F gpios)
• powerstage:
  • fully synchronous buck/boost topology (all drivers discrete)
  • switching frequency somewhere between 48 kHz and 48.1 kHz
  • switching deatime: arounf 420 ns everywhere
  • Power transistors:
  • AON6420: Nmos
  • AON6748: Nmos, datasheet does not exists, DK suggests AON6354 as replacement
• LCD:
  • 16x2, white backlight
  • 12 pin FFC
  • SPI communication @ 310 kHz with dedicated (probably) Data/Command signal (often called 4-wire SPI in LCD docs)
  • MCU has no SPI on those pins -> bitbanging :facepalm:
  • switched backlight
• LM324 opamps at cell Vsense, probably all fully differential
• no external analog mux for ADC

Photos

Removing sticker reveals 2 screws. After unscrewing, case opens.

XT60 connectors prevent PCB removal. They are almost impossible to remove. Easiest solution is removal i small piece of plastic case blocking Input XT60 connector.

I can shoot more photos if anyone is interested in specific details.

Captures

SMPS

full sigrok capture and pulseview session

LCD

full sigrok capture and pulseview session