4 ms·

Seems like Mini-PCI Express is a bit overkill for this, wonder why they chose that form factor instead of like direct-serial (for embedding) with a usb-serial f

Seems like Mini-PCI Express is a bit overkill for this, wonder why they chose that form factor instead of like direct-serial (for embedding) with a usb-serial for all the rest.

LeifCarrotson 4y ago
It is using direct 3.3V serial for embedding, the mini PCIe is just used for the ubiquitous, effective, cheap, and low profile connector. It doesn't actually have any PCIe lanes, it has power, ground, the aforementioned 3.3V serial, a transmit/receive indicator, and a single (!) GPIO. I'm not 100% sure, but I suspect if you tried to plug it into an mSATA slot either it or the laptop would be damaged.
- LeifCarrotson 4y ago
  Edit: Here's the pinout of the Swarm modem: https://i.imgur.com/VQvDrEa.png https://i.imgur.com/VQvDrEa.png Here's the pinout of a mini PCIe card: https://i.imgur.com/YJIyJ86.png https://i.imgur.com/YJIyJ86.png And here's the pinout of mini PCIe/mSATA (numbered from bottom to top, which makes it slightly more challenging to compare): https://i.imgur.com/7yL3FW4.png https://i.imgur.com/7yL3FW4.png The ground connections all line up, and the 3.0 to 5.0V input, 1000 mA rated VDD on the Swarm is connected to 3V3. The Swarm UART is connected to REFCLK+ and REFCLK- on the PCIe bus, and the GPIO drives LED_WWAN. Should be no problem! I suppose that it would be really cool if they provided an I2C/2-wire/SMB communication interface on pins 30 and 32 so hypothetically you could connect it to a computer.
wolrah 4y ago
> wonder why they chose that form factor instead of like direct-serial Because MiniPCIe is a common formfactor for cellular modems, so this could be swapped in to existing devices with no hardware changes and minimal software changes. The slot carries not only a lane of PCIe but also a channel of USB 2.0 and SIM connections. Most cellular modems entirely ignore the PCIe and just use it in USB mode, which I assume this is doing as well. Personally I'd have chosen M.2 as MiniPCIe is outdated, but I also would not at all be surprised to find that the industrial IoT world they're targeting has kept using the deprecated standard because some major vendor got a great deal on MiniPCIe connectors when the mainstream computing world switched to M.2. Considering how many devices designed well after the introduction of MicroUSB or even USB-C I still come across with MiniUSB connectors I feel like that's a common thing in the niche computing device world, intentionally and knowingly making new things using the obsolete connector to save a few cents per unit.
- jpm_sd 4y ago
  The vast majority of industrial/embedded hardware is still on mPCIe. I have only started seeing M.2 in these applications in the last few years, believe it or not.
MisterTea 4y ago
Because MiniPCIe also provides a USB channel in addition to PCIe which is what this modem uses.

Seems like Mini-PCI Express is a bit overkill for this, wonder why they chose that form factor instead of like direct-serial (for embedding) with a usb-serial for all the rest.

LeifCarrotson 4y ago

It is using direct 3.3V serial for embedding, the mini PCIe is just used for the ubiquitous, effective, cheap, and low profile connector. It doesn't actually have any PCIe lanes, it has power, ground, the aforementioned 3.3V serial, a transmit/receive indicator, and a single (!) GPIO. I'm not 100% sure, but I suspect if you tried to plug it into an mSATA slot either it or the laptop would be damaged.

LeifCarrotson 4y ago
Edit: Here's the pinout of the Swarm modem: https://i.imgur.com/VQvDrEa.png https://i.imgur.com/VQvDrEa.png Here's the pinout of a mini PCIe card: https://i.imgur.com/YJIyJ86.png https://i.imgur.com/YJIyJ86.png And here's the pinout of mini PCIe/mSATA (numbered from bottom to top, which makes it slightly more challenging to compare): https://i.imgur.com/7yL3FW4.png https://i.imgur.com/7yL3FW4.png The ground connections all line up, and the 3.0 to 5.0V input, 1000 mA rated VDD on the Swarm is connected to 3V3. The Swarm UART is connected to REFCLK+ and REFCLK- on the PCIe bus, and the GPIO drives LED_WWAN. Should be no problem! I suppose that it would be really cool if they provided an I2C/2-wire/SMB communication interface on pins 30 and 32 so hypothetically you could connect it to a computer.

wolrah 4y ago

> wonder why they chose that form factor instead of like direct-serial Because MiniPCIe is a common formfactor for cellular modems, so this could be swapped in to existing devices with no hardware changes and minimal software changes. The slot carries not only a lane of PCIe but also a channel of USB 2.0 and SIM connections. Most cellular modems entirely ignore the PCIe and just use it in USB mode, which I assume this is doing as well. Personally I'd have chosen M.2 as MiniPCIe is outdated, but I also would not at all be surprised to find that the industrial IoT world they're targeting has kept using the deprecated standard because some major vendor got a great deal on MiniPCIe connectors when the mainstream computing world switched to M.2. Considering how many devices designed well after the introduction of MicroUSB or even USB-C I still come across with MiniUSB connectors I feel like that's a common thing in the niche computing device world, intentionally and knowingly making new things using the obsolete connector to save a few cents per unit.

jpm_sd 4y ago
The vast majority of industrial/embedded hardware is still on mPCIe. I have only started seeing M.2 in these applications in the last few years, believe it or not.

MisterTea 4y ago

Because MiniPCIe also provides a USB channel in addition to PCIe which is what this modem uses.