MicroPython Forum (Archive)

The Pyboard D schematics show pin numbers from 1 to 40.

Attached is mashed-together image where I overlaid a pyboard D (both sides semi transparent) onto a 50mil grid to help me better visualise where the WBUS connectors are relative to other things on the board. I couldn't find something similar pre-existing. This is just done by eye, so take it with a pinch of salt. It is not definitive. Perhaps others will find it useful.

Notes:

• I have only drawn the central 40 pins of each WBUS connectors, not the two extra mystery (mechanical/electrical/redundant?) connectors that are sometimes seen as an extra pair of pins at each end of the connector.
• The WBUS pins are drawn with metric 0.4mm pitch, meaning that the y-value of the uppermost pin on either connector is 0.4mm*(19/2) = 3.8mm ..... which in is about 2.992 squares on my 50 mil grid -- which is why they appear to line up with a gridline, even though they don't. (3x50mil is 3.81mm).

pythoncoder wrote: ↑

Fri May 08, 2020 6:48 am

The Pyboard D schematics show pin numbers from 1 to 40.

Plus pins 81, 82, 83, 84! I counted the contacts on my PYBD and there are definitely 44 contacts in that connector.

There is a photo with some dimensions on it here:
https://store.micropython.org/media/pro ... F2_ds3.jpg

According to Hirose specs the four extra pins on the 40 pin connectors are only for mechanical stability. They can't be used as extra contacts.

chuckbook wrote: ↑

Sun May 10, 2020 3:10 pm

According to Hirose specs the four extra pins on the 40 pin connectors are only for mechanical stability. They can't be used as extra contacts.

Can you provide a link to the "Hirose specs" you are looking at, and perhaps a pointer where to find that statement in the doc?

I'm looking at https://www.hirose.com/product/document ... =D31649_en and right at the top it shows a photo of a 40-pin connector and there are 40 contacts, unlike the 44 contacts visible on the PYBD. The document mentions the "style B" of the connector "with reinforcing metal fitting" and that adds 4 extra pads to solder the connector down to the board, but they are clearly separated from the rest of the 40 contacts, see page 4 "recommended PCB layout" right figure.

Ah, mystery solved after checking the measurements with a caliper: what's on the PYBD is the header, not the receptacle. Page 10 of the doc linked in the previous post applies. It has "Note 3 : Use the contacts at the four corners as metal fittings. Do not use them as signal or power contacts." So it's really a 44 contact header but the receptacle apparently only has 40 contacts (I don't have a daughter card to check) and the 4 corner contacts on the header are actually mechanically not fully accessible (some of the end plastic overlaps them a bit). Confusing stuff!

I started to have some unpredictable behaviour with my custom PYBD carrier board, and discovered that I needed a little finger pressure on the PYBD to get consistent electrical contact through all the pins of these connectors (this is a professionally manufactured board, not a home solder job). It has been working fine for months until now. I 3d-printed a "clothes peg" style clamp to hold it in place, which is working fine for now. I also have noticed that the PYBD is a lot easier to insert & remove than it was originally - it used to "click" into place, not so much now.

Anyone else notice that the specs for these connectors show durability as 30 mating cycles..?

I hope this is a one-off with my setup and not a limitation with these connectors... I have cycled different PYBD's on/off this board quite a number of times that's for sure.

If a PYBD doesn't 'click' into position there is no guarantee for proper contact of all pins.
Although HIROSE only specifies 30 mating cycles (-35° to 85° C), the connectors will easily withstand more than 1000 cycles at room temperature.

I made a motherboard with two wbus receptacles into which a pyboard-d connects as a controller.

Unfortunately the first time I tried to unplug the pyboard, one of the wbus receptacles disintegrated, leaving about 50% of its pins soldered to the motherboard and free of the plastic casing, while the other 50% parted company from the board and left with the receptacle which stayed attached to the pyboard.

The fact that some of my wbus receptacle pins separated from the pcb suggests my soldering job was not good. However, the fact that the ones which WERE soldered well stayed there but slipped out of the receptacle worries me.
Do any of you have experience of the best ways of keeping wbus receptacles firmly attached to the pcbs they are on? I don't have the ones with extra metal pads just for mechanical stability. I have tried injecting small wantities of superglue under the connectors. but it just wickes up around all the pins creating a terrible mess in the area you want to keep clean.