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====== Ikoka Stick Meshtastic Device ======

GitHub repository: [[https://github.com/ndoo/ikoka-stick-meshtastic-device]]

===== Ikoka! (行こか!) =====

"行こか?" or "行こか!" is [[https://en.wikipedia.org/wiki/Kansai_dialect|Kansai dialect]] for "shall we go?" or "let's go!".

I hope that building these long-range Meshtastic designs inspires you to go on your next [[https://en.wikipedia.org/wiki/DXing|DXing]] adventure.

===== Features =====

  * LoRa
    * Up to 33 dBm (2 W) output power
    * 410–493 MHz (433 MHz band) or 850–930 MHz (868/915/923 MHz band)
  * Bluetooth 5 LE
  * Wi-Fi 4 (2.4 GHz)
  * Lithium-ion battery with charging
  * 0.96" OLED display

Feature set above depends on part selection.

==== Hardware ====

==== Parts Selection ====

Several options are available depending on the feature set you need.

=== Microcontroller ===

  * [[https://www.seeedstudio.com/Seeed-XIAO-BLE-nRF52840-p-5201.html|Seeed Studio XIAO-nRF52840]] - Bluetooth 5/LE
  * [[https://www.seeedstudio.com/XIAO-ESP32S3-p-5627.html|Seeed Studio XIAO-ESP32-S3]] - Bluetooth 5/LE and Wi-Fi 4 (2.4 GHz)

=== LoRa Module ===

  * [[https://www.cdebyte.com/products/E22-400M22S|E22-400M22S]] (410–493 MHz at 22 dBm)
  * [[https://www.cdebyte.com/products/E22-400M30S|E22-400M30S]] (410–493 MHz at 30 dBm)
  * [[https://www.cdebyte.com/products/E22-400M33S|E22-400M33S]] (410–493 MHz at 33 dBm)
  * [[https://www.cdebyte.com/products/E22-900M22S|E22-900M22S]] (850–930 MHz at 22 dBm)
  * [[https://www.cdebyte.com/products/E22-900M30S|E22-900M30S]] (850–930 MHz at 30 dBm)
  * [[https://www.cdebyte.com/products/E22-900M33S|E22-900M33S]] (850–930 MHz at 33 dBm)

=== Lithium-ion Battery (4.2V charging termination, optional) ===

  * 21700 Lithium-ion battery cell (4.2V charge termination; holder: [[https://www.beilamoo.com/sdm/1074412/4/pd-5180803/21061576-2986071/ONE_21700_Battery_Holder_with_Surface_Mount_SMT.html|BeilaMoo PA21700*1-SMT]]/[[https://jlcpcb.com/partdetail/Myoung-BH_21700B1BJ001/C20606791|MYOUNG BH-21700-B1BJ001]])
  * Lithium-polymer pouch battery cell (4.2V charge termination; connector: Molex PicoBlade 1x02P, pitch 1.25mm)
  * Do not use both a 21700 and LiPo battery simultaneously, they will be shorted together in parallel

== Wiring for Battery Charging ==

You will need a PicoBlade Female-to-Pigtail cable assembly such as Molex [[https://www.molex.com/en-us/products/part-detail/2181120200|218112-0200]]. A compatible cable ships with Heltec Wireless and LILYGO LoRa products so you probably have spares you can use. [[https://muzi.works/products/battery-cable-molex-picoblade|Muzi Works]] and [[https://store.rokland.com/products/battery-connector-cables-battery-wires-jst-1-25-5pcs-for-lilygo-and-heltec|Rokland]] also sell compatible cables.

  - Trim the pigtail length to around 5cm if it is longer
  - Strip 2mm of insulation from each pigtail, then twist and tin the wire strands
  - Solder the red pigtail (or pin 1) to the BAT+ pad on the back of the XIAO module
  - Solder the black pigtail (or pin 2) to the BAT- pad on the back of the XIAO module
  - Plug the cable into the XIAO Charger connector on the Ikoka Stick

In my previous design, the [[https://github.com/ndoo/ikoka-nano-meshtastic-device|Ikoka Nano]], the XIAO module was SMD soldered onto the board, while the BAT+ pad was soldered through a plated through-hole via. However, the actual solder joint is buried and couldn't be inspected for continuity, quality and ensuring the BAT+ pad was not shorted to the BAT- pad.

In the interest of ease-of-assembly and keeping the XIAO module interchangeable, while not wasting the built-in battery charging circuit on XIAO modules, this approach was chosen instead.

=== OLED Display (Optional) ===

  * Generic SSD1306 0.96" OLED display modules with 2.54mm pin headers [[https://www.aliexpress.com/item/1005008077705181.html|(AliExpress)]]

===== Firmware =====

==== GPIO Assignment ====

^XIAO Pin^Function              ^XIAO-nRF52840^XIAO-ESP32-S3^
|1 (D0)  |User button           |2 (P0.02)    |1            |
|2 (D1)  |EBYTE E22 - DIO1      |3 (P0.03)    |2            |
|3 (D2)  |EBYTE E22 - RST       |28 (P0.28)   |3            |
|4 (D3)  |EBYTE E22 - BUSY      |29 (P0.29)   |4            |
|5 (D4)  |EBYTE E22 - SPI NSS   |4 (P0.04)    |5            |
|6 (D5)  |EBYTE E22 - RXEN      |5 (P0.05)    |6            |
|7 (D6)  |SSD1306 OLED - I2C SDA|43 (P1.11)   |43           |
|8 (D7)  |SSD1306 OLED - I2C SCL|44 (P1.12)   |44           |
|9 (D8)  |EBYTE E22 - SPI SCK   |45 (P1.13)   |7            |
|10 (D9) |EBYTE E22 - SPI MISO  |46 (P1.14)   |8            |
|11 (D10)|EBYTE E22 - SPI MOSI  |47 (P1.15)   |9            |
|12      |SSD1306 OLED - 3.3V   |3V3          |3V3          |
|13      |GND                   |GND          |GND          |
|14      |NC                    |5V           |5V           |

==== Meshtastic Compatibility ====

The XIAO module is intended to be socketed with pin headers/pin sockets, to allow swapping out modules depending on what features are needed (Bluetooth, Wi-Fi, different power consumption profiles, etc.); Compatibility with official Meshtastic firmware depends on the inserted XIAO board.

=== XIAO-nRF52840 ===

  * EBYTE E22 LoRa
    * LoRa pins are identical to the officially-supported [[https://www.seeedstudio.com/XIAO-nRF52840-Wio-SX1262-Kit-for-Meshtastic-p-6400.html|Seeed Xiao NRF52840 Kit]] on [[https://flasher.meshtastic.org/|Meshtastic Web Flasher]]
    * LoRa will work out of the box on officially-supported firmware
    * Special consideration must be taken if using the E22-900M33S module
      * Set the transmit power to Γëñ 9 dBm on first use (when setting the LoRa region)
      * **Transmit power must never be set greater than 9 dBm** to avoid damaging the module's RF frontend
  * SSD1306 OLED I2C
    * Pin D6/P1.11 and D7/P1.12 are [[https://github.com/meshtastic/firmware/blob/152b8b1b0235bc461c6e4451fbcdac0987b8bf90/variants/seeed_xiao_nrf52840_kit/variant.h#L137-L138|reserved for the L76K GPS module in the officially-supported variant]]
    * A custom firmware must be built to define these pins as I2C (TODO)
  * User button
    * Pin D0/P0.02 is [[https://github.com/meshtastic/firmware/blob/152b8b1b0235bc461c6e4451fbcdac0987b8bf90/variants/seeed_xiao_nrf52840_kit/variant.h#L144|reserved for the L76K GPS module in the officially supported variant]]
    * A custom firmware must be built to define this pin as the user button (TODO)

==== XIAO-ESP32-S3 ====

  * Pin definitions are different from the officially-supported [[https://www.seeedstudio.com/Wio-SX1262-with-XIAO-ESP32S3-p-5982.html|Seeed Xiao ESP32-S3 Kit]]
    * This is because Seeed uses GPIOs on the 30-pin board-to-board press-fit connector instead of the standard XIAO pins
    * A custom firmware must be built (TODO)

===== PCB Renders =====

==== PCB Top ====

{{https://ndoo.github.io/ikoka-stick-meshtastic-device/top.png|top}}

==== PCB Bottom ====

{{https://ndoo.github.io/ikoka-stick-meshtastic-device/bottom.png|bottom}}

==== Rotating GIF ====

{{https://ndoo.github.io/ikoka-stick-meshtastic-device/rotating.gif|animation}}

(Rendered with [[https://github.com/linalinn/kicad-render|kicad-render]].)
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