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23n27.bsky.social

@23n27.bsky.social

break apart to build anew • unrepentant eureka moment junkie • aspiring abstraction-leak plugger and black box elucidator n621.de / The other network: dgc.social/@23n27

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23n27.bsky.social @23n27.bsky.social · 30/09/2026

A project from the bucket list: Some lab automation tooling. (Bottom side stacking connector is still in the mail so I'm bodging this with an IDC cable)

A stack of two PCBs, the top one containing 7 relay channels

View of the top board. It just feeds data and power from the bus interface (RJ45) into the stack but can also inject power into the bus and has an USB interface to optionally drive (and optionally power) it, so it can be used in a self-contained fashion too.

Relay board with 7 channels, each containing a DPDT relay that connects to a shared bus.

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23n27.bsky.social @23n27.bsky.social · 28/02/2026

Maybe I should try projectposting on here? Anyway, this seems to be working, so I guess I need to do the fully integrated version with a GPS module now.

Two PCBs connected with a flat flex cable. The left one has a USB-C cable plugged in, the right one an Ethernet cable.

The left one is a breakout for the AX88772C USB->RMII chip.

The right one is a breakout for the DP83640 PTP Ethernet PHY. It has a bunch of GPIOs broken out to pin headers and has two SMA jacks (one for PPS input, one for the frequency generator output of the PHY).

A bunch of cables are soldered to the EEPROM and (invisibly) the MDIO test points on the AX88772C board and go off to the top of the picture into a basic FX2 logic analyzer.

Screenshot of dmesg:

usb 3-12.4.3: new high-speed USB device number 66 using xhci_hcd
usb 3-12.4.3: New USB device found, idVendor=0b95, idProduct=772b, bcdDevice= 0.02
usb 3-12.4.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 3-12.4.3: Product: grandmaster-on-a-stick
usb 3-12.4.3: Manufacturer: isentropic.systems
usb 3-12.4.3: SerialNumber: 000000
PTP clock support registered
asix 3-12.4.3:1.0 (unnamed net_device) (uninitialized): PHY [usb-003:066:01] driver [TI DP83620 10/100 Mbps PHY] (irq=POLL)
TI DP83620 10/100 Mbps PHY usb-003:066:01: attached PHY driver (mii_bus:phy_addr=usb-003:066:01, irq=POLL)
asix 3-12.4.3:1.0 eth1: register 'asix' at usb-0000:80:14.0-12.4.3, ASIX AX88772B USB 2.0 Ethernet, 00:00:10:00:1d:02

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