Particle Mesh hardware update: important changes in the final product

Connectivity BLE // NFC
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Originally published at: https://blog.particle.io/2018/08/03/particle-mesh-hardware-update-important-changes-in-the-final-product/

The hardware designs for the Argon, Boron, and Xenon are final. A lot of engineering and design has happened since we started taking preorders for Particle Mesh hardware in February and we want to share with you the changes we’ve made to improve all of the Particle Mesh dev kits.

TL&DR

All three dev kits have more flash memory and PWM pins than we originally planned. The Argon has some special design changes to its Espressif Wi-Fi chip and now requires an external antenna — not to worry, it's now included.

The Argon, Boron, and Xenon get More flash memory

We increased the flash memory on the Argon, Boron, and Xenon from 2MB SPI flash to 4MB SPI flash. This increase will give you more space for your programs and comes at no additional cost to you.
  • Design plan: 2MB onboard SPI flash
  • Final hardware: 4MB onboard SPI flash

The Argon, Boron, and Xenon get More PWM pins

We've doubled the number of PWM pins from 4 to 8. With PWM pins you can do things like fade LEDs and control servo motors. Having more makes building easier.
  • Design plan: 4 PWM pins
  • Final hardware: 8 PWM pins

Additional Argon-only changes

The Argon will come with more flash and PWM pins that you can use just like the Boron and Xenon. But there are two changes that are specific only to the Argon: the Wi-Fi coprocessor and the antenna configuration.

Final Argon Wi-Fi Coprocessor

The Argon final design uses the Espressif ESP32-D0WD 2.4G Wi-Fi coprocessor with 4MB of on-board flash dedicated to the ESP32. This is a dual-core version of the ESP32 with more memory than its single-core variant.
  • Design plan: Espressif ESP32-S0WD 2.4G Wi-Fi coprocessor with 1MB flash
  • Final hardware: Espressif ESP32-D0WD 2.4G Wi-Fi coprocessor with 4MB flash

While the dual-core of the Espressif ESP32-D0WD is not user accessible, the additional 4MB flash on the chip allows room for future Wi-Fi improvements.

Final Argon Antenna Configuration

During the initial design we wanted the onboard PCB antenna to be user selectable between the Nordic mesh/Bluetooth radio and the Espressif Wi-Fi radio. Unfortunately, after testing our engineers concluded that implementing a second RF switch resulted in too much signal degradation and did not produce the high performant user experience we wanted.
  • Design plan: user selectable onboard PCB antenna between the mesh/Bluetooth and Wi-Fi
  • Final hardware: onboard PCB antenna for mesh/Bluetooth and a provided external antenna for Wi-Fi

In the final design of the Argon the mesh/Bluetooth radio uses the onboard PCB antenna and the Wi-Fi radio uses an included external antenna. While this might be disappointing to some, our goal is to provide you with the best possible connectivity experience. Dedicating the onboard antenna for mesh/Bluetooth and requiring an external for Wi-Fi meets our high standards.

There is still time to add to your preorder. Remember, once the preorder phase closes in a few weeks board prices will increase. And don’t forget, you can follow the Particle Mesh timeline to see what goes into building our next generation of hardware and software.

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This is great news.

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Considering having to have a big external antenna sounds like it’ll be pretty unwieldy, and obviously wasn’t what was originally specified, how do you cancel a preorder?

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You can cancel your preorder using the support portal.

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Is there a picture of the new Argon available?

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@dcschelt I am eagerly awaiting the date the Argons and Xenons I have ordered will ship. I am currently using Photons with headers on a mother board and as a first step would like to build an adaptor board to be pin compatible between the Argon/Xenon and Photon headers. Where and when will I be able to see the final pinouts for the?

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Hi @armor,

It sounds like our Classic Adapter might work for you.

Also, here’s a pinout of the Xenon that we published in our mesh timeline.

Xenon-pinout-lock
Xenon-pinout-lock894×505 196 KB

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Thanks - looks like the classic adaptor is for Argon/Xenon to Electron rather than Xenon to photon. There seems to be a couple of differences from the Adafruit FeatherWing pinout i.e.
ARf => MD/Mode
GND=>NC

Are these explained anywhere yet?

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You should leave the MODE/MD pin unconnected in your design. It’s connected to the MODE button, which has a pull-up on it.

You would use this if you wanted to connect an external button to enter setup mode.

It’s not a perfect fit for the use of AREF, but it’s not a horrible match and it frees up a pin for use by GPIO.

AREF - this is the Analog Reference if there is one for the chip. If there is not, keep this pin not-connected. We recommend Wings don’t require this pin as not all chips have external ARef’s.

Do you the pin next to TX for GND=>NC?

'Free' Pin - This is the pin to the right of TX. You can use it for an extra GPIO or if you have some onboard module that has a useful breakout. Sometimes we tie it to ground. Do whatever you like! FeatherWings should not require or use this pin unless there's some really good reason.

The Argon/Boron/Xenon don't use this pin, you can tie it to ground or leave it unconnected.

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Wow, thanks for the fast reply.

Since I am powering photons on 5V via Vin - this should connect to VUSB?

Enable on Xenon would connect to GND on Photon

Also, SCK = > A3, MOSI =>A5, MISO=>A4 so presumably Xenon A3, A4, A5 can be either DAC, WKP or NC?

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If a shield is meant to accomodate an Electron it will also take a Photon (and vice versa) since both are pin compatible.

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Fair point, but it means 2 x 6 pins hanging in mid air. Also, looks like female headers on both sides whereas I want emulate a photon with headers. I guess for $5 it is worth putting up with such things as I could not get equivalent made for such a price :slight_smile:

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I couldn't find the schematics for the classic adapter, so I don't really know exactly how the mappings were done. Some are obvious (D2 -> D2) but some could be mapped more than one way, and I don't know how it was done.

Since I am powering photons on 5V via Vin - this should connect to VUSB?

Yes, with one really important caveat. Unlike VIN on the Photon and Electron, there is no diode on VUSB - it's connected directly to the USB connector VBUS so you should never power both the VUSB pin and the USB connector.

In most Feather wings, VUSB is meant to be 5V power from the USB connector into the wing, but you can feed power the other way (with caution).

Enable on Xenon would connect to GND on Photon

The Xenon EN pin determines whether the Xenon powers the 3V3 pin. If low, 3V3 is not powered. If high, the 3V3 is powered by the Xenon and a Feather wing can use 3.3V power between 3V3 and GND

Also, SCK = > A3, MOSI =>A5, MISO=>A4 so presumably Xenon A3, A4, A5 can be either DAC, WKP or NC?

On the Xenon, there are dedicated pin for SCK, MOSI, MISO. For example, SCK is D13, not A3. I'm not sure how the classic adapter maps A3 - A5, it could do so either as analog pins or as SPI pins and it's not clear what was done.

There is no DAC on the nRF52840 so if you need a DAC, you'll need an external I2C or SPI DAC. However presumably A6/DAC maps to A6 on when using the classic adapter as it still can be used for ADC.

The nRF52840 is much more flexible on pin mapping so any pin can be a wakeup pin, not like the STM32Fxxx that require the dedicated WKP pin to wake from deep sleep.

The picture of the classic adapter is wrong. It was a pre-production sample and they accidentally soldered female headers on the bottom. They should be male.

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