RP2040 zero

When the PICO2 came out, I bought a couple of PiMoroni 2350 boards, both smaller than official PICO2 boards, one with USB-C and fewer pins, one with full set of pins but no USB port on-board ... life intervened so done nowt with them ... I remember hearing there's something b0rked with I/O on the 2350s in general, not sure if it's just edge cases or generally f***ed?

That could cause some issues if you're doing a drop in replacement for a RP2040 but if you use stronger external pullup/pulldowns it should avoid the issue.

It looks like they haven't done a respin to fix it thus far.

Theo

Ah. But the boards I am talking about have allegedly pukka RP2040 chips on them

It's OK...I take it no one here has used them. Well I'll report back when I have. So far all I did was plug one in and fire up with bootselect button pushed. It looked like a Pico does.

Lightweight too. 1.75g

Thanks.

the BusPirate folks had issues with their BP5XL boards and needed to junk a batch, I see that redesigned as the BP6 it's now on sale ...

Yes, that's the kind of application where it's a problem. You attach GPIOs to random stuff and intend to probe what's there. That means you flip through the internal settings for input/output/pullup/pulldown and listen out to how the input changes.

The leakage affects that kind of application badly (input pins should be high impedance but they aren't here) but if you are putting the chip in a board where you already know what's on the other end of the pin, you can design the circuit appropriately.

RPis are more likely to be used in situations where you take the MCU and plug in and out random things onto the pins which are affected by it, compared with other MCUs where they only ever get put on vendor PCBs where everything is predetermined in the schematic. So it's really a hobbyist focused problem rather than a wider problem.

Theo

All my Pis end up on my design of PCB where stuff is either disabled or its strictly controlled

I cant see why anyone would enable an input pin and leave it floating. Its simply bad design

If you're making a logic analyser, that's what you do. That's effectively what the Bus Pirate is. (It will also generate some of the protocols it analyses, but that's a different feature)

Anyhow they didn't leave the pins floating - they enabled the onboard pulldown resistor. The problem is that the pulldown has unexpected side effects.

Theo

I bought using firefox np

NO. given that the logic analyser would most likely want to be 5V you would have the inputs pulled down externally with a resistor in series.

AFAIAC as a electronic engineer anything that isnt exnternally connected is 'floating'

What costs 77p ?

Cheapest showing now is 3.37 for two, minimum order for free postage is £8 otherwise postage is probably £1.99 but it doesn't actually say.

I can still see a price of 77p each for two (including VAT) with free shipping. For an extra 18p each you can also get an RP2350 board.

John

There is something called “tristate”.

Two RP2040 boards with free P&P, actually it's gone down to 76p today (I think the dollar price was 99ç so that's probably currency fluctuation, still comes up with a vague error when I press "buy".

Aliexpress knocks a few bucks off the price of everything as a 'welcome deal' if you aren't logged in. If you login as an existing customer the prices go up. If you are a new customer and try to order lots of stuff, you might find the 'welcome deals' only apply to the first item(s) you buy.

I think all the Chinese sites do that - I ordered something from wish.com for $18 when everywhere else was selling it for $36, and I think that was their new customer discount. I think Temu is the same.

Theo

I'm logged in, with name/address/currency/payment methods all shown from my account and the 2x RP2040 in my cart, showing the 76p total.

It just says "Order unsuccessful, There may be an internet issue. Close the app and restart to try again."

It's not the first time I had issues with aliexpress, my firefox used to hate their "slidy thing" on the logon dialogue.

Only thing I had that was undeniable s*it were some darlingtion power transistors that blew up an amp and eventually a loudpseaker.

Not enough voltage rating compared to what was stamped on them.

It was like going back to the good old days of Sinclair Radionics with his 'super' rejected transistors rebadged as 'Sinclair 101s' or whatever.