Neil Hao

Starts from 2022/May/31 to 2024/03/17 00:46 (Last Modification)

The Station G1 has been discontinued and has been replaced by the Station G2. Meshtastic Mesh Device Station G2 is an upgraded design of Station G1, using the latest ESP32 S3 MCU. As an RF research project, Station G2 also brings key updates in RF. The primary RF design goal of Station G2 is to improve the Lora receiving sensitivity by about 4dB based on a dedicated Ultra-Low Noise Figure LNA. Also increase the transmit power and improve Signal to Noise ratio of short data packets by designing the Fast-Transient DC-DC for 35dBm Lora PA.

Edition Comparisons between our Meshtastic Products

Meshtastic can send off-grid message using inexpensive hardware to create your personal mesh.

The Station Edition series is a compact Lora device with high power PA (Maximum TX Power: 35dBm@915MHz or 868MHz for Station G1 Edition), Rugged SMA Antenna Socket, rich external IO interface, wide input voltage range (8VDC-20VDC). This series aims to provide the best RF performance in all series with credit card size and rugged construction. Fixed-location base stations and vehicle-mounted base stations are typical application scenarios for this series.

For the firmware, all Station Edition devices come with pre-installed Meshtastic firmware. Meshtastic Mesh Device Station Edition G1 also had been supported by the official meshtastic repository on Github. More detials could be found in the The Latest Firmware section.

Station Edition could be powered by either USB Type C (PD Protocol with minimum 9V2A is required, 15V2A is recommended due to the requirements of 12V Battery Docker) or 2Pins Socket (Pitch=2.5mm, 8VDC-20VDC, 2A minimum).

Wide voltage input makes the Station Edition ideal as an vehicle-mounted base station and powered directly from the in-vehicle 12V system. The USB Type C power input allows the device to be easily powered by a USB Type C adapter which supports the PD protocol.

Ability to increase transmit power makes it possible to balance communication distance and communication speed. For low power meshtastic devices, usually necessary to set the modem to Long/Slow to obtain the required communication distance, but when using this setting, the communication speed will be very slow, and the continuous sending of messages will also cause timeouts. By increasing the transmit power, we can set the modem to Long/Fast or even Medium/Fast to get a similar experience to Internet-based instant messaging software.

More information about modem setting: https://meshtastic.org/docs/settings/config/lora

Similar as Nano Edition, the Station Edition is also constructed by stacking up PCB boards.This method offers a good balance of cost and mechanical strength. The Station Edition employs an aluminum substrate PCB (sliver) as heat sink for high power lora PA. Nonelectrical conductivity high performance thermal grease is applied between the heat sink and the main PCB. Front Side and Bottom Side of the case.

Instrument Setup and Device Under Test (DUT) configuration For Instrument Setup, RF Explorer 6G Combo PLUS Spectrum Analyzer and 40 dB Attenuator was used to measure the RF transismission power. Meshtastic firmware firmware_neil_station-g1-1.2.60.bin.zip was flashed into the DUT. Meshtastic Android APP 1.2.64 had been used to control the DUT with channel options = “Long Range / Slow” and Region = “US”.

Measurements When SX1262 TX set to 16 dBm, according to above result, the RF output power was 35.5 dBm, Gain = 19.5dB.

Repeat the measurement process with various SX1262 TX Power (TX Power Setting). The results were summarized in the follow table.

Summary for Conduction Test

Because Station Edition G1 could be powered by either USB Type C (PD Protocol with minimum 9V2A is required) or 2Pins Socket (Pitch=2.5mm, 8VDC-20VDC, 2A minimum). Power supply choice is very convenient, so that Battery Docker has been discontinued.

12V Battery Docker is powered by USB TypeC with 15V PD Protocol. It has capability to charge 3*18650 Lithium Batteries with 2A MAX charging current. It also comes with multi protection features, such as Battery Temperature Monitoring, Overcharge/Overdischarge protection, Overcurrent Protection, etc.

While the Station G1 can be powered directly via USB TypeC, the 12V Battery Docker can still be used as backup power, or in scenarios that require mobility.

The motivation for designing the 12V Battery Docker is that most Power Banks cannot supply power to Station G1, because the Power Bank will automatically power off when the load is low in power consumption, especially when PD protocol is used. A few hundred mA would be considered as low in power consumption for most cases.

Charging Status LEDs:

• Batteries are full charged when Green LED ON and Red LED OFF.
• Batteries are charging when Green LED OFF and Red LED ON.
• Green LED and Red LED are OFF at the same time indicates the 12V Battery Docker is powered up by voltage lower than 15V. Generally, this status indicates that the Type C Charger does not support 15V PD Protocol.
• Green LED and Red LED flashing at the same time indicates two possible problems. 1. At least one of three 18650 batteries is not installed properly or damaged. 2. The charging voltage is lower than the batteries voltage (12.6V MAX) which typically means your USB Type C Charger supports PD protocol but does not support PD 15V. In other words, it usually means that the output voltage of the USB Type C Charger has fallen back to 12V or 9V (determined by the maximum output voltage the USB Type C Charger supports), you may have to replace the USB Type C Charger with one which supports 15V PD Protocol.

According to the charging profile in the CN3703’s datasheet, the highest temperature was expected to occur in the phase with the highest current, thus the highest temperature could be measured during the Constant Current Phase (2A for 12V Battery Docker).

For the charging experiment, three 2000 mAh 18650 Li-ion batteries was installed into 12V Battery Docker. The charging process used 1 hour and 23 minutes to charge the batteries’ voltage from 9.6V to 12.6V. About half an hour was Constant Current Phase, and the rest of the time was Constant Voltage Phase.

Thermal infrared image of the Constant Current Phase (Left) and the Constant Voltage Phase (Right), ambient temperature: 28 degrees in Celsius

Summary for Thermal Analysis

The battery gauge will be automatically enabled within 30s if CN2 connector is connected to CN2 of Station G1. For Station G1, the battery voltage has been mapped from 0-12.6V.

Details

The battery characteristics are defined at Line 37 to Line 40 in the variant.h.

#define BAT_FULLVOLT 12600
#define BAT_EMPTYVOLT 8200
#define BAT_CHARGINGVOLT 12600
#define BAT_NOBATVOLT 6690

So that, Station G1 is expected to work with three Li-ion 18650 batteries, the full charged voltage = 12.6V, empty voltage = 8.2V.

Known Issues

The firmware will automatically turn off the device when detecting the battery voltage lower then 8.2V. On the other hand, the battery voltage will drop 0.X V when the PA is in transmission mode, because the PA will theoretically consume peak value of 1.2A@7.5V. Therefore, in daily use, you cannot wait for the battery voltage to drop to 8.2V before charging. The exact value of the voltage drop depends on the internal resistance of the batteries. Choosing batteries with lower internal resistance can alleviate the problem.

Warning

If you want to set the PA Output Power higher or equal to 33dBm. Please use the coaxial extension cable with magnetic base adapter included with product or any 50 ohm coaxial cable to keep the antenna at least 20cm away form the battery docker. Otherwise, the XB3303A Li-ion Battery Protection IC on the battery docker may be interfered and enter the protection state, so that Station G1 will be powered off. The power can be restored by reinstalling all batteries.

When you install new firmware, the previous configuration may be lost. You may need to refer to TX Power Setting to set TX Power again.

Typical Settings

PA Output Power = 29.5 dBm

meshtastic --set lora.tx_power 8

PA Output Power = 34.5 dBm

meshtastic --set lora.tx_power 14

Meshtastic Mesh Device Station Edition G1 had been supported by the official meshtastic repository on Github from firmware version 1.3.42. Thus, the latest firmware could be downloaded from the meshtastic project’s releases page: https://github.com/meshtastic/Meshtastic-device/releases

Firmware file: firmware-station-g1-1.x.x.bin

Following instructions to flash it to the Station g1: https://meshtastic.org/docs/getting-started/flashing-firmware/esp32/

The Android APP could be downloaded and installed from the Google Play Store: https://play.google.com/store/apps/details?id=com.geeksville.mesh

APP Source Code: https://github.com/meshtastic/Meshtastic-Android/releases

The iOS APP could be downloaded and installed from following URL: https://meshtastic.org/docs/software/apple

Javascript, Python, Web Interface are also supported by the Meshtastic. More information: https://meshtastic.org/docs/software

Prerequisites

1. The latest version of Meshtastic Python
2. The latest version of Meshtastic Firmware

Execute following command by using Meshtastic CLI, this operation will set the SX1262 TX Power to 14 dBm:

meshtastic --set lora.tx_power 14

Output:

Connected to radio
Set lora.tx_power to 14
Writing modified preferences to device

Verification, execute following command:

meshtastic --get lora.tx_power

Output:

Connected to radio

lora.tx_power: 14
Completed getting preferences

According to the Summary for Conduction Test, the PA Output Power is expected to be 34.5 dBm (2.82 W), after executing above command.

Prerequisites

1. Meshtastic Python 1.2.95
2. Meshtastic Firmware 1.2.65Patch1

Execute following command by using Meshtastic CLI, this operation will set the SX1262 TX Power to 14 dBm:

meshtastic --ch-set tx_power 14 --ch-index 0

Output:

Connected to radio
Set tx_power to 14
Writing modified channels to device

Verification, execute following command:

meshtastic --info

Output:

Connected to radio
...
Channels:
  PRIMARY psk=default { "txPower": 14, "modemConfig": "Bw125Cr48Sf4096", "psk": "AQ==" }
...

According to the Summary for Conduction Test, the PA Output Power is expected to be 34.5 dBm (2.82 W), after executing above command.

Any RF device can transmit encrypted data in the ISM bands without license. However, the maximum transmitter power fed into the antenna should be less than or equal to 30dBm (1W).

Benefit from high power PA even when operating in the ISM bands. For example, if there is a long coaxial cable between the transmitter and the antenna, the coaxial cable may have considerable insertion loss. At this time, the transmitting power of the transmitter can be increased to ensure exactly 30dBm power feeding into the antenna.

Reference

• FCC Rules for Unlicensed Wireless Equipment operating in the ISM bands. Retrieved Jun 1, 2022, from https://afar.net/tutorials/fcc-rules/

Lora 915MHz is exactly 33cm band in the amateur bands. With Amateur Radio License, according to the National Association for Amateur Radio's description, the transmitter can transmit unencrypted data using up to 1500W.

This official document describes in detail how to turn off Meshtastic's encryption: Licensed (HAM) Operation.

How to increase the Lora RF output power: TX Power Setting Copyright: The National Association for Amateur Radio

Reference

• US Amateur Radio Frequency Allocations. Retrieved Jun 1, 2022, from http://www.arrl.org/frequency-allocations
• US Amateur Radio Technician Privileges. Retrieved Jun 1, 2022, from http://www.arrl.org/files/file/Tech%20Band%20Chart/US%20Amateur%20Radio%20Technician%20Privileges.pdf
• Amateur Radio Allocations and Overlapping Part 15 Bands - An Overview and a Part 97 versus Part 15 and Permissible Power Comparison. Retrieved Jun 28, 2022, from https://www.qsl.net/kb9mwr/projects/wireless/allocations.html