SP108E HardwareAnalysis - seurat-atreides/Sonoff-Tasmota GitHub Wiki

So far I analyzed it is equipped with these chips:

  • ESP-12F
  • STM32F-030C8T (Cortex M0)
  • Winbond 25Q32 (EEPROM)
  • 74HC245
  • XL1509 3.3E1 (Step down regulator)
  • RX/TX of STM is connected to ESP.
  • 74HC245 buffers the outputs

ESP is connected to the STM RX/TX pins. No other connections seen. We can assume there is some firmware in the STM that does the low level connection to the LEDs.

Question is how does the ESP communicate with the STM and what exactly does the STM at all. But we can mod the hardware so the ESP can talk to the LEDs.

I made some pictures with phone and microscope.

PCB

sp108e-board

Open the housing, see the red marks for the holders)

sp108e-openhousing

RX/TX connection ESP to STM

sp108e-rxtx-

STM32F0

sp108e-stm32

EEPROM

sp108e-eeprom

Pins lead to the STM32F0 (Firmware flash? Debug?)

st108e-stm-32-externalconnections

ESP-12 and its pins

sp108e-esp-1

sp108e-esp-2

Buffer chip 74HC245

p108e-hc245

Traces on bottom side from STM to HC245 (actually R3 and R4)

sp108e-traces-to-hc245

For the hardware mod to make it working without the STM32F0, there are several ways:

1. Cut traces and add wires

We need to break one of the traces on the bottom of the PCB. Then connect GPIO4 of ESP-12 with R4. Also RX/TX connection between STM32F0 and ESP-12 need to be broken up.

2. Hold STM32F0 in reset

This is the simpler method, no cuts on the PCB required, just two additional wires.

  • NRST of STM32F0 to GND
  • IO4 of ESP-12 to R4

See here for details.

Flashing prohibited

Major problem right now is that IO0 is directly connected to VCC, so we cannot bring ESP-12 into flash mode. Working on a solution.