GT Power B6 mini status #338

diggit · 2023-05-19T22:22:54Z

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 🤦
- 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.