We have been trying to define what is a *HDR board and this is what we decided on:
It is as small is possible.
It is breadboard friendly with 0.1" headers.
Requires 3.3V to run. If other voltages are needed then they are included.
The USB client pins are optionally exposed but a micro USB connector is added for convenience.
The USB power is exposed on one of the pins.
Not all pins maybe exposed on the pads where the headers mount. This is to keep the size reasonably small.
if the HDR is made for a SoC then castellated holes (similar to the side pads on the G120 SoM) are added, making the HDR also an SoM option for that SoC. In this case, expose as many pins as possible but having all is not required. This is to keep the size small.
Doesn’t this contradict your reasoning for not including the voltage regulator on the G30HDR? I thought it was a good idea to give the option to run at lower levels as long as its spelled out clearly in the catalog how it works. This isn’t the case currently with the G30HDR.
#2 actually puts some constraints on this one. I’ve been wondering if you shouldn’t think more along the lines of a standard size & pinout such that HDRs could be replaced with newer modules w/o having to change the carrier board similar to how the G400-D works. Larger chips could extend pins length-wise but perhaps the first 40 pins are standard?
@ ianlee74 - 3.3V is required to be added by the user is what I mean but if the board internally required 1V for example then we will include this, but not the 3.3V. This is better for devices that run at lower voltages and can so be powered directly from a battery. So yes we are on the same page here.
We were not thinking carrier boards as HDR boards will be of all random sizes. G30HDR and G400HDR can’t be to be size compatible, not even similar.
I’m thinking specifically the SoC HDR boards which people could use like SoMs in a header socket. The SoM HDR boards are a bit of a different beast. I wouldn’t imagine anyone using those in sockets.
@ Gus - I get confused with the difference between a breakout board and a HDR board. And now a carrier board…
I think a diagram would help define relationships would help. For example, a SoC would go on a carrier board which would go on a breakout board… Or a SoC would go on a Module which go on to ?
@ Mike -
SoM is something like G120 and G400S
SoC is something like G30 and G80
The HDR board is technically a breakout board of the SoM or SoC.
The carrier board is the the customer’s custom board, that will host the SoM or SoC.
A carrier board is typically holding the SoM or SoC on it but, in some rare cases, the HDR can be placed right on the carrier board.
lets have the RTC crystal discussion again, can we ? OK, maybe not, but the G30HDR locks that function unusable since there’s no footprint and no simple way to achieve tacking it on. If the intent of the *HDRs are to give a breadboardable way to use a device as if you’d include it in your own product (using SoC or SoM), that is a restriction that I personally don’t like.
Otherwise, I see the *HDR as a small form-factor stand-alone device to prove the * works in your use-case and is breadboard friendly. If it doubles as a solder-in module (eg G30HDR) then that’s a bonus - just make sure you think about via protection if you haven’t already done so
@ Brett - if we are adding the rtc crystal then why not add a battery holder? And why not add an sd connector? And while we are at it, few gadgeteer sockets
No seriously, why rtc crystal but not sd connector? Or anything else…The sd is just an example.
I agree, it’s a scope creep problem. Sure, SD would be nice too, thanks ! But really, that’s not easy for a “breadboard friendly” mounting either, you’d never fit it on the G30HDR let alone in a way that didn’t impact the headers.
For me, RTC is the one thing that should be kept close to the pins on the processor, which is why I see it as important to have footprints for.
I like the HDR boards and concept behind them, they are compact and easy enough to prototype(with pin headers) and [em]should be[/em] ready to use out of the box. (include the regulator 8) )(like Cerb40 II) They also seem practical for low to mid volume implementation.
Also, my vote is for the rtc crystal and caps included on the board. It saves header pins too. And if you can break out the SD pins that would be cool too.
@ Gismofx - the SD pins are always exposed but the question was if we are adding the RTC on the board then why not add the SD connector? The answer was: First, the RTC needs short pins so it may not work right on the header pins. Also, you will save 2 pins from the header making room for other signals.
