PCIe Support on Tachyon

Tachyon comes with one PCIe connector, wired up for a PCIe 3.0 x1 (1-lane) interface. That means you’re getting up to 1 GB/s of theoretical peak bandwidth — enough to power NVMe SSDs, USB expansion hubs, and a variety of other PCIe goodies. No configuration needed — it’s enabled by default. Just plug and play!

Hardware Overview

Tachyon is built around the Qualcomm QCM6490 chipset, which actually supports two lanes of PCIe 3.0 under the hood. But to keep things simple — and compatible with the Raspberry Pi PCIe ecosystem — we’re exposing just one lane via the PCIe connector.

There’s a dedicated 5V boost regulator powering the PCIe interface, and it shares that 5V line with the 40-pin header. Why a boost regulator? So that even if Tachyon is running on a 3.7V battery, your PCIe devices still get a clean 5V power supply. 💡

You can also turn PCIe power on or off in software, giving you more control and efficiency in battery-powered projects.

⚡ Power Tip: The maximum current draw is 2A, and that’s shared between the PCIe port and the 5V pin on the 40-pin header. So if you’re using both a HAT and a PCIe peripheral, double-check their combined draw — make sure it stays well below that 2A limit!

PCIe Connector Pinout

Hardware Setup

Connecting PCIe Devices

Tachyon includes a dedicated PCIe interface via an FPC (Flat Printed Cable) connector, allowing you to hook up high-speed peripherals like NVMe SSDs, AI accelerators, or custom boards.

In this guide, we’ll walk through connecting a PCIe NVMe HAT as an example.

Start with the PCIe NVMe HAT ready and the FPC cable included in your NVMe kit.

Step 1: Open the Retention Clip

Gently lift the retention clip on the FPC connector. Avoid forcing it—these are delicate.

Step 2: Insert the Cable

Take your FPC cable and insert it into the connector.

✅ Make sure the pin contacts are facing away from the clip (typically down toward the PCB).

Gently push the cable in until it’s fully seated.

Step 3: Close the Clip

Re-insert the retention clip to lock the cable in place. It should feel firm—not forced.

Double-check that the cable is straight and fully seated with the latch properly locked.

Caution:

Before powering up your Tachyon, always verify the cable orientation on both ends.
Incorrectly connected PCIe cables can damage both the Tachyon and the attached device.

Once connected and secured, your PCIe device should sit flush and aligned. Now you're ready to boot! Power on the Tachyon, the NVMe base Power LED should come on shortly after Tachyon is powered on.

Software setup

Examine PCIe devices with lspci

lspci
00:00.0 PCI bridge: Qualcomm Device 010b
01:00.0 Network controller: Qualcomm Device 1103 (rev 01)
00:00.0 PCI bridge: Qualcomm Device 010b
01:00.0 PCI bridge: ASMedia Technology Inc. Device 1182
02:03.0 PCI bridge: ASMedia Technology Inc. Device 1182
02:07.0 PCI bridge: ASMedia Technology Inc. Device 1182
04:00.0 Non-Volatile memory controller: Phison Electronics Corporation Device 5021 (rev 01)

PCI bridge 0 is the internal connection to the WiFi/Bluetooth SoC. PCI bridge 1 is the external PCIe connector. Here we can see the NVME controller has been detected.

We can see a block device has been created at /dev/nvme0n1. We can examine it with lsblk
```
lsblk | grep nvme0n1
nvme0n1 259:35   0 953.9G  0 disk
```

We can format the drive with fdisk. Generally the options are n for new partition, p for primary partition, defaults for sector start and end, and finally w to write and quit.

sudo fdisk /dev/nvme0n1
[sudo] password for particle:

Welcome to fdisk (util-linux 2.34).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table.
Created a new DOS disklabel with disk identifier 0x06a8f583.

Command (m for help): n
Partition type
   p   primary (0 primary, 0 extended, 4 free)
   e   extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-2000409263, default 2048): 2048
Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-2000409263, default 2000409263): 2000409263

Created a new partition 1 of type 'Linux' and of size 953.9 GiB.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

Format the new partition, this may take some time depending on the size of your disk

sudo mkfs.ext4 /dev/nvme0n1
mke2fs 1.45.7 (28-Jan-2021)
Found a dos partition table in /dev/nvme0n1
Proceed anyway? (y,N) y
Discarding device blocks: done
Creating filesystem with 250051158 4k blocks and 62513152 inodes
Filesystem UUID: 5520786a-782e-4715-9165-3334f4f0f931
Superblock backups stored on blocks:
	32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
	4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
	102400000, 214990848

Allocating group tables: done
Writing inode tables: done
Creating journal (262144 blocks):

done
Writing superblocks and filesystem accounting information: done

Mount the new partition

sudo mount /dev/nvme0n1 /mnt/

The NVMe drive is now available for use

lsblk | grep nvme0n1
nvme0n1 259:35   0 953.9G  0 disk /mnt

Troubleshooting

Forcing Bus Re-enumeration

To force scanning of the PCIe root complex in order to detect new devices

echo 1 > /sys/bus/pci/rescan

Drive Write Testing

Drive write speed can be tested with the dd utility

sudo dd if=/dev/zero of=/mnt/test.bin bs=4k iflag=fullblock,count_bytes count=1G
262144+0 records in
262144+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 4.60684 s, 233 MB/s

Supported HATs

NVMe drives and USB hubs generally work without any additional drivers. Some specific boards that have been tested are:

Hardware Overview​

PCIe Connector Pinout​

Hardware Setup​

Connecting PCIe Devices​

Step 1: Open the Retention Clip​

Step 2: Insert the Cable​

Step 3: Close the Clip​

Software setup​

Troubleshooting​

Forcing Bus Re-enumeration​

Drive Write Testing​

Supported HATs​