Caution
The GND of the JK-B GPS port is directly connected with the B- of your battery. Even if your BMS is in protection or stopped you can measure the full voltage between this GND and B+. This therefore presents a risk of bypass of the BMS P- and can be dangerous if the GND of your ESP32 is connected to the GND of your inverter or a measurement shunt for example.
I therefore strongly advise you to achieve galvanic isolation between your ESP32 and the UART-TTL of the JK-B GPS port.
Caution
V1 and V2 must be isolated and cannot come from the same source. V1 (JK GPS port side) can be powered by the 3V3 of the ESP32 via a DC-DC isolator (B0303S = 3V3-to-3V3), V2 (ESP32 side) is powered directly by the 3V3 of the ESP32.
┌────────────┐ | ┌──────────┐ ┌───────────┐
│ | └─3V3--V1>│ |<V2---3V3---<| |
│ DEVICE │<RX-------AO<│ UART-TTL │<AI-------TX<| ESP32 |
│ JK BMS │>TX-------AI>│ ISOLATOR │>BO-------RX>| |
│ │<----GND---->│ │<----GND---->| |
└────────────┘ └──────────┘ └───────────┘
Here are some components available on the market allowing you to set up galvanic isolation. The UART-TTL isolator 2 seems a little better isolated with more space below the chip.
| UART-TTL isolator | DC-DC isolator |
|---|---|
 |
 |
| M5Stack RS485 unit (isolated) |
|---|
 |
Caution
The diagram below does not show the galvanic isolation of the UART-TTL connection !
The GPIOs are preconfigured in the packages/board/board_atom-s3-lite.yaml file.
You need to import this YAML into the main YAML.
UART-TTL RS232-TTL CAN BUS
┌──────────┐ ┌──────────┐ ┌────────────┐ ┌──────────┐
│ │<TX------RX>│2 5│<TX-------TX>| | | |
│ JK-BMS │<RX------TX>│1 6│<RX-------RX>| CA-IS3050G |<---CAN H --->| Inverter |
│ │<----GND--->│ ESP32 │ | CAN |<---CAN L --->| |
│ │ 5V---->│5V 3V3| | | | |
└──────────┘ └──────────┘ └────────────┘ └──────────┘
Caution
The diagram below does not show the galvanic isolation of the UART-TTL connection !
The GPIOs are preconfigured in the packages/board/board_atom-lite.yaml file.
You need to import this YAML into the main YAML.
UART-TTL RS232-TTL CAN BUS
┌──────────┐ ┌──────────┐ ┌────────────┐ ┌──────────┐
│ │<TX------RX>│26 22│<TX-------TX>| | | |
│ JK-BMS │<RX------TX>│32 19│<RX-------RX>| CA-IS3050G |<---CAN H --->| Inverter |
│ │<----GND--->│ ESP32 │ | CAN |<---CAN L --->| |
│ │ 5V---->│5V 3V3| | | | |
└──────────┘ └──────────┘ └────────────┘ └──────────┘
Caution
The diagram below does not show the galvanic isolation of the UART-TTL connection !
The GPIOs are preconfigured in the packages/board/board_esp32-devkit-v1.yaml file.
You need to import this YAML into the main YAML.
3V3 CAN bus
UART-TTL RS232-TTL CAN BUS (3V3)
┌──────────┐ ┌──────────┐ ┌────────────┐ ┌──────────┐
│ │<TX------RX>│16 23│<TX-------TX>| | | |
│ JK-BMS │<RX------TX>│17 22│<RX-------RX>| SN65HVD230 |<---CAN H --->| Inverter |
│ │<----GND--->│ ESP32 │<----GND---->| CAN |<---CAN L --->| |
│ │ 5V---->│VIN 3V3│<----3V3---->| | | |
└──────────┘ └──────────┘ └────────────┘ └──────────┘
5V CAN bus
UART-TTL RS232-TTL CAN BUS (5V)
┌──────────┐ ┌──────────┐ ┌────────────┐ ┌──────────┐
│ │<TX------RX>│16 23│<TX-------TX>| | | |
│ JK-BMS │<RX------TX>│17 22│<RX--4K7--RX>| TJA1050 |<---CAN H --->| Inverter |
│ │<----GND--->│ ESP32 │<----GND---->| CAN |<---CAN L --->| |
│ │ 5V---->│VIN VIN│<----5V----->| | | |
└──────────┘ └──────────┘ └────────────┘ └──────────┘
UART-TTL RS485 RS485-TTL RS232-TTL CAN BUS
┌──────────┐ ┌───────────┐ ┌────────┐ ┌─────────┐ ┌─────────┐ ┌──────────┐
│ │<----TX---->│Y JK Y│<A------A+>│ │<TX-----RX>│16 23│<TX-------TX>| | | |
│ JK-BMS │<----RX---->│W RS485 W│<B------B->│ RS485 │<RX-----TX>│17 22│<RX--4K7--RX>| TJA1050 |<---CAN H --->| Inverter |
│ │<----GND--->│B Adaptor B│<---GND--->│To 3.3V │<---GND--->| |<----GND---->| CAN |<---CAN L --->| |
│ │<----VBAT-->│R │ │ │<---3V3--->| ESP32 |<----5V----->| | | |
└──────────┘ └───────────┘ └────────┘ └─────────┘ └─────────┘ └──────────┘
The GPS port sometimes called RS485 is not an RS485 port but 3V3 UART-TTL.
# UART-TTL GPS port on JK-BMS (4 pin, JST 1.25mm pitch)
┌─── ─────── ────┐
│ │
│ O O O O │
│GND RX TX VBAT│
└────────────────┘
│ │ │ | VBAT is full battery volatge eg 51.2V (possible to use it via an isolated DC-DC converter)
│ │ └──── to TTL-isolator AI (input)
│ └──────── to TTL-isolator AO (output)
└──────────── to TTL-isolator GND
The UART-TTL (labeled as GPS) socket of the BMS can be attached to any UART pins of the ESP.
A hardware UART should be preferred because of the high baudrate (115200 baud).
The connector is called 4 pin JST with 1.25mm pitch.
