Powering Starlink REV4 (V3) from the 12V without PoE injector/router

My 12V mod for the REV3 is extremely popular. Today, I will show you how to make a similar modification with the new terminal REV4 (a.k.a V3).
As always, a lot of pictures below.

The new terminal is quite challenging to disassemble, but it’s possible. Just don’t rush.
All PoE and primary DC-DC step-down circuits in the new terminal are placed on a separate board. This board is fixed on the backplate and connected to the primary board via an unusual 2mm pitch connector.

The need for a separate board is likely due to the need to place the connector at the base of the complex back cover. An aluminum plate behind the PS board is a heatsink bot for the PS board and SoC on the primary PCB.

Unfortunately, I couldn’t identify the type of this connector. It’s a standard 2mm pitch header with additional plastic stands for better fixing. It’s possible to use a standard 2mm header like this one.

This connector (let’s call it a “system connector”) carries various signals: supply voltage, I2C, and Ethernet.

Additionally, the power supply board ground plane is connected to the primary PCB via spring plates and capacitors in series. This helps to create a short path for the high-frequency currents.

Power supply board

Let’s look at the power supply board components.

The input jack is connected to the Ethernet magnetics via a PCB-mounted ferrite bead.
Ethernet data from the transformer is routed directly to the system connector. TVS diodes are placed on the primary PCB. Supply voltage passes a few diodes that protect from reverse polarity and voltage spikes.

The PoE detection circuit generates a signature that helps the PSU (router) detect connected Dishy and provide a 57V supply. An upcoming article will discuss this further.

The primary step-down is built around the well-known LM5146, equivalent to the L3751 used in the REV3 terminal. The layout and principle of the operation are the same.

The STM32 MCU (SpaceX calls it “sense” mcu) monitors voltage and current incoming. It runs protected SpaceX firmware and is accessible via the terminal’s I2C bus.
A special script in the Dishy firmware checks controller presence and updates its firmware if necessary.

Depending on the current operating mode, the controller uses different addresses on the I2C bus:
– Bootloader: 0x62
– Boot ROM: 0x63
– SpaceX application: 0x55

The current sensor is based on a low-value resistor and operation amplifier and is connected to the MCU ADC input.

Bosch BME280 temperature/humidity sensor is configured to address 0x76 and connected to the same I2C bus. But it seems currently unused (as of the end of July 2024). At least I haven’t noticed any requests to the sensor address.

Here is a block diagram of the power supply board:

You may have noticed an additional current shunt near the inductor. However, it seems connected only to the unpopulated area on the top of the board. I have no idea why it’s there.

System connector

This is the pinout of the connector:

SDA/SCL pins are connected directly to the Starlink SoC and used for communication with the sense MCU and BME280.

Reset and Boot0 are simple GPIO lines of the SoC that reset the sense MCU and switch it to bootloader mode. You can ignore these lines.

Ethernet lines are intended to be connected to the Ethernet transformer. The colors are for reference.
Please never connect this bus directly to an Ethernet cable.

Lame 12V mod

The easiest way to convert to 12V is to remove the big inductor and connect wires directly to the GND and 12V bus on the PCB.

Nothing more is required. It will run fine on 12V and the sense MCU will be powered and accessible.

Please always connect a positive wire to the inductor’s pad. This will help optimize the buffer capacitors’ usage.
The negative wire should be soldered directly to the connector. This will bypass the current sensor and eliminate any overcurrent alerts and triggers.

The allowable voltage range is 10-16V. It will survive voltage spikes around 17V, but I wouldn’t recommend running it long on higher voltages.
Please note there is no reverse-polarity protection. Wrong polarity will kill your Dishy.

Running without the power supply board

It’s possible to run the terminal without this power supply board. The current firmware doesn’t care about the absence of the sense MCU.

As an experiment, I used my EtherMod board, which was hardwired to the PCB. It works without any issues.

A note about testing without the router and App

The web interface on 192.168.100.1/dishy.starlink.com has been dead for a long time. SpaceX didn’t have the resources to support it, so they abandoned it.
Direct access to the gRPC API is the easiest way to test Dishy running without the router and mobile App. We can use grpcurl for this.

Getting the current status of the terminal (a.k.a. debug data):

grpcurl -plaintext -d {\"get_status\":{}} 192.168.100.1:9200 SpaceX.API.Device.Device/Handle

The most critical sections in the output:

Ethernet is running at full speed:

 "ethSpeedMbps": 1000,

All components are up and running:

"readyStates": {
    "scp": true,
    "l1l2": true,
    "xphy": true,
    "aap": true,
    "rf": true
},

GPS is ok:

"gpsStats": {
    "gpsValid": true,
    "gpsSats": 7
},

The Starlink terminal can enter the network and reach the ground PoP:

"initializationDurationSeconds": {
    "burstDetected": 63,    <<<< Detect signal burst from the satellite
    "firstCplane": 77,      <<<< Received control data package
    "firstPopPing": 108,    <<<< Successful ping of the ground PoP
    "gpsValid": 71,
    "initialNetworkEntry": 75,   <<<< Entered the network
    "networkSchedule": 82,  <<<< Received network schedule from the SpaceX "orchestrator"
    "rfReady": 50
},

REV4 Power Hat

I built a better prototype to prove the concept.

The central element is the same EtherMod. The ceramic capacitor array helps eliminate voltage drops when long wires are used.

Fits and works nicely:

Finally, I designed a custom “power hat” PCB.

The schematic is below. You may have noticed the lack of ESD protection. We don’t need these extra components since they are on the primary PCB.

The PCB is double-sided, but all components are only on the top side.

Gerber files.

Current consumption

Lower voltage means higher current, and REV 4 is power-hungry. Without heaters, you should expect 8+ A spikes over the 12V bus.

When heating, the current consumption may exceed 15A with active data transmission.
Despite this, 12V conversion may save you some percent of the power.

Thanks for reading!