Jonathan,

Thanks for your email on this topic.

These connectors mainly eat up a lot of board space. Reducing the pin count to something more realistic should befit all.

Every pin you have in a connector is a potential reliability issue. Reliability in the actual connection interface and in the increase of complexity of the electrical design.

Each pin with routed signals requires more effort to rout signals on the PCB.

These connectors are adding mass to one side of the CubeSat moving the center of gravity. This will effect the orbital dynamics and stabilization systems.

Some AMSAT designs use multiple bus systems, RS232, I2C, CAN, IO signals. These busses require different interface chips, power voltages, power consumption, firmware, and user knowledge. Reducing to a single communication bus system would reduce pin count, chip count, power needs and improve reliability.

The connector systems marketed are not all equal. If a 104 pin standard is used then there should also be a specification for which connector are to be used. This will define the pin size, plating layers - nickel gold, socket sizes and pin hardness. I suggest using the pin size that is soldered in place. If the press pin socket pins/holes are used then they should be soldered after assembly.

During prototype and production of flight hardware these connectors are difficult to work with. Each board/connector will have to be disassembly and reassembly many times.

We need Battery voltage, and an I2C (2 pins) possibly a signal ground, and possible a hard reset signal.

Bob

On Apr 7, 2023, at 9:26 AM, Jonathan Brandenburg via pacsat-dev pacsat-dev@amsat.org wrote:

Following up on last night's conversation...

When there is talk about CubeSats using the PC-104 standard, what that really means is the use of the PC-104 form factor in terms of board size, mounting hole placement, and the 2x2x26 connector. CubeSats don't adhere to any of the signalling or protocol aspects of PC-104 standards (including additional connectors defined in the PC-104 standard).

There hasn't been any standards body define this form factor for Cubesats (as far as I know) so I imagine it just sort of grew organically from the first university satellites looking around for something to copy and noticed the small form-factor computer.

As correctly noted, CubeSats don't standardize the use of the pins in the PC-104 connector but it seems like component manufacturers looked around to see how others had been using pins and followed suit. Thus if PACSAT is using I2C, power, and ground pins there will be little conflict. What I've seen is CubeSat component manufacturers offer an option sheet that allows the customer to select from a set of options. Along the lines of "put I2C pins here or there or do not connect" kind of options.

I hear the comments about how "This a large connector!" and "How many pins are really needed?" and "How are they used by different components?" All that is true. At same time it's also true that if somebody is adding a component to their CubeSat it will most likely expecting boards with the PC-104 form factor. AMSAT is an exception but even then we had to partially adapt our boards to the PC-104 form factor for use by non-AMSAT organizations.

When I'm at CubeSat Developers Workshop later this month, I'll do a survey. While I will see at least one university eschew the PC-104 form factor (because they're developing ALL the components in-house and prefer a plug-in-slot configuration because it simplifies assembly a lot) I expect most will have purchased the bus (including structure, C&DH, EPS, and any ADCS) which will be in the PC-104 form factor. But I could be surprised and the tide may be turning.

Comments?

Jonathan

-- Jonathan Brandenburg, KF5IDY

---

pacsat-dev mailing list -- pacsat-dev@amsat.org View archives of this mailing list at https://url.emailprotection.link/?buUg7YY4HZLXKo6ZKNudC8bRTBdOsBlAV5C9rq-aqx... To unsubscribe send an email to pacsat-dev-leave@amsat.org Manage all of your AMSAT-NA mailing list preferences at https://url.emailprotection.link/?bO71JCUf8Kb7txAlIoAarNqcIdQhyb8VQQIN4j0Gik...