ESP-igate v3 aka the iGate that finally talks to an iPhone

The iGate firmware for dsTNCv2 has some history behind it. The first version was written by Krzysiek SP9SKP for the ESP01 module and served well for years - unfortunately the sources got lost and only the binaries remained. So I rewrote the whole thing from scratch, and since I was already deep in that code, I also moved it to something newer than the ESP01: the Seeed XIAO ESP32-C6. The module is the size of a fingernail, costs about as much as two coffees, and brings WiFi, BLE 5, 4 MB of flash and its own USB.

The real reason was more specific than "because it's newer", though. Android users have APRSDroid and Bluetooth Classic SPP - that has worked forever. But iOS does not expose SPP at all, so there is no way to talk to an iPhone that way, neither through an HC-05 nor through any other BT module. The only route is Bluetooth Low Energy. The ESP01 has no BLE, the ESP32-C6 does - hence this version. The iGate exposes KISS over BLE as a Nordic UART Service, and the phone sees it as an ordinary TNC.

Resources got more comfortable along the way. On the ESP01 the modem occupied the only UART, so the diagnostic log had to go out over the network. On the C6 the USB is a separate piece of hardware, the modem has its own UART, and I can watch the console over the cable and over UDP at the same time. The configuration moved from a hand-calculated flash sector into NVS, so there is no more guessing where the SDK keeps its own data.

Current project status

RF → APRS-IS iGate with a range filter and a duplicate filter
Bidirectional iGate - messages from APRS-IS go out on RF to stations heard locally
WIDEn-N digipeater with callsign substitution (WIDE2-2 → MYCALL*,WIDE2-1)
Third-party packet de-tunneling and retransmission in normal format
TNC over TCP server - KISS or TNC2 (text), up to 2 clients at once
KISS over BLE - Nordic UART Service, iPhone/iPad, up to 2 clients
BLE ↔ APRS-IS gating in both directions, each direction its own switch
Position beacon, APRS messaging with acknowledgements
Web UI with configuration and status, configuration stored in NVS
Log over USB-CDC and over UDP multicast (239.199.9.1:9199)
On-board antenna or U.FL connector - selectable in the configuration

Note: this is a fresh release, straight after the port. If you hit something odd - drop me a line and I'll fix it.

How to wire it up

Everything at 3V3 levels, common ground, 19200 8N1. Three wires plus ground:

XIAO D6 (GPIO16)  ---->  dsTNCv2 modem RX
XIAO D7 (GPIO17)  <----  dsTNCv2 modem TX
XIAO D3 (GPIO21)  <----  modem CTS (HIGH = ready, LOW = busy)
                         * input with an internal pull-up *
GND               -----  GND

CTS is pulled up, so if you forget that wire the iGate will consider the modem permanently ready and transmit blindly. Better to connect it - the dsPIC drops a frame if a second one enters its UART while the first is still being transmitted.

Gating directions

Three independent switches on the APRS tab. Only the first one is enabled by default, so BLE behaves like an ordinary TNC:

Switch	Default	What it does
BLE → RF	on	a frame from the phone goes on the air
BLE → APRS-IS	off	a frame from the phone goes to the network - path ends with TCPIP*, the server adds the q-construct
APRS-IS → BLE	off	the whole stream from the server filter handed to the phone as KISS

That last direction is the reason this exists at all: a phone with no cellular coverage gets the full APRS-IS traffic through the iGate, over BLE. The iGate filters out echoes so the same frame does not land on the map twice - once from the air, once from the network.

Downloads

ESP-igate v3.0 firmware dated 2026-08-28 - XIAO ESP32-C6, WiFi + KISS over BLE * LATEST *
firmware for the old ESP01 - on the dsTNCv2 page, for those who have an ESP01 soldered in and do not want to change anything

The archive holds two bin files: factory (bootloader + partition table + application, flashed from zero) and app (application only, for updates without touching the configuration), a flash.sh script and a short README.

FAQ

How do I flash the firmware?
The XIAO has USB-C and needs no programmer at all. On Linux:

esptool.py --chip esp32c6 --port /dev/ttyACM0 --baud 460800 \
    write_flash -z 0x0 esp-igate_v3.0_factory.bin

An update, without touching the bootloader:

esptool.py --chip esp32c6 --port /dev/ttyACM0 --baud 460800 \
    write_flash -z 0x10000 esp-igate_v3.0_app.bin

If the board refuses to be caught, enter the bootloader by hand: hold B, click R, release B.

What is the WiFi password and how do I set it up?
Exactly as on the old ESP01: after flashing, the module starts in configuration mode and brings up a network with SSID:dsTNC and password 123456789. The web UI sits at 10.0.0.1. Connect to that network, enter your own WiFi credentials, callsign, APRS-IS passcode and position. DHCP is on by default, but a static address can be assigned as well.

Can I use WiFi and BLE at the same time?
Yes - and that is the biggest difference from the old arrangement. With the ESP01 and an HC-05 you had to choose: either WiFi or Bluetooth, because those were two different modules for one socket. The C6 handles both in parallel. The 2.4 GHz radio is shared, so both sides lose a little when you push large files through, but APRS traffic is a few frames per second and there is nothing to fight over.

How do I connect an iPhone?
You need an app that speaks KISS over BLE. The iGate advertises itself as dsTNC and exposes a Nordic UART Service:

service  6E400001-B5A3-F393-E0A9-E50E24DCCA9E
RX       6E400002-B5A3-F393-E0A9-E50E24DCCA9E  (write - phone to iGate)
TX       6E400003-B5A3-F393-E0A9-E50E24DCCA9E  (notify - iGate to phone)

Those are the standard NUS UUIDs, so in most apps it is enough to pick the ready-made "Nordic UART" preset instead of typing anything in by hand. I use my own iOS app, still polishing it - once it is fit for other people, I will add a link here.

Why not a plain ESP32 with Bluetooth Classic, so APRSDroid works?
Because an iPhone would still not see SPP - iOS does not expose that profile to apps. I would have to pick whose life gets easier. Android is not left out though: there is a TNC over TCP server (port 8001 by default, KISS or TNC2), and APRSDroid connects over the network just as happily as over Bluetooth. On top of that, a phone over BLE and a computer over TCP can be connected at the same time - both get the same traffic.

Can I hook this up to a radio with a built-in TNC, without a dsTNCv2?
Yes, as long as the radio can put KISS or TNC2 out on a serial port - for example a Kenwood TM-D710 (with its TNC switched into KISS mode) or a newer Yaesu such as the FTM-510; how exactly to switch the data port is a question for the manual of your particular model. The firmware detects on its own whether it is receiving KISS frames or TNC2 text lines, so there is nothing to set there - the port speed goes into the web UI.

What you do have to sort out is level shifting to 3V3. The COM port on Kenwoods is RS-232 with real RS-232 levels, so something like a MAX3232 is needed; if the radio has a 5 V logic port, a level shifter or a divider is enough. The critical direction is the one into the ESP: 5 V, let alone 12 V from RS-232, applied straight to a C6 pin ends with replacing the module. The other way round is gentler, since 3V3 out of the ESP is usually enough for the radio input to read as a high.

There is nothing to connect the CTS line to in such a setup, and nothing needs to be - the input is pulled up, so the iGate will treat the transmitter as permanently ready. For a receive-only iGate that makes no difference. If you turn on the digipeater or gating of APRS-IS messages out to RF, keep in mind that without CTS the iGate has no idea when the radio's TNC is transmitting and may push a frame into it mid-transmission. The dsTNCv2 does have that line, which is why it is the safer pairing.

Does the old ESP01 stop working?
No. The ESP8266 firmware stays where it was and can still be flashed - the links are on the dsTNCv2 page. New work will happen on the C6 though; maintaining two versions of the same code is a road to bugs in both.

On-board or external antenna?
The XIAO has both: a ceramic one on the board and a U.FL connector. The on-board one is active by default. The switch is in the web UI on the Network tab and needs a reboot. If you pick the external one, make sure an antenna is actually screwed on - transmitting into an open connector is not healthy for the front end.

My configuration disappeared after an update - what happened?
That is normal if the configuration format changed in the new firmware. The structure carries a version number, and on a mismatch the module comes up with factory defaults - better that than reading old data as new and then explaining why the iGate transmits somewhere it should not. Callsign, passcode and position have to be entered once more.

Where do I get the module?
The XIAO ESP32-C6 is an off-the-shelf Seeed Studio product, available from them or from the usual electronics shops. There is nothing to solder here beyond the three wires to the dsTNCv2.

If you have questions - feel free to drop me a mail. Keep in mind though that I have plenty on my plate and may answer with some delay :-) 73! DE Tomek, SP9UOB.

If you like my project, you can support it with a donation: