Re-Using M.2. connectors Micromod and BlackEdge/Alloy

[Folknology]

This is interesting from Sparkfun 'MicroMod' They have re-used the M.2 connector to allow a kind of 'Core' Module and standard carriers. I have considered using the M.2 connector for BlackEdge but never executed. I am intrigued by what you think of both the M.2 re-use , Sparkfun's implementation and the idea of a BlackEdge or Alloy M2, let me know your thoughts..

[lawrie]

Would the idea be to just use the physical connector, or to follow that pinout. The pinout doesn't look a very close match to what we would want for an FPGA-based board.

[Folknology]

Well I am considering this from many angles, appreciate all ideas etc..

However you are quite right, their pin choice does suck somewhat, my choice would go something like:

1. Dedicated pins SDA,SCL,RX,TX,MOSI,MISO,SCK,CS
2. Mixed sig pins for Analog + low bandwidth (bitbang/PWM) capability (at least 6 maybe a few more)
3. The rest Fast Digital IO pins to make busses/SDIO,QSPI as required (FPGA pins)

[Folknology]

I was thinking about a BlackIce (IceCore) MicroMod with their pinout. I would connect as follows:

1. SPI, I2C0, CAN, Uart 2, DX/PWMX/ADC * 4, ADC*2, SWD & USB Device connected to STM32l433
2. Ice40 connected to I2S, GX/Bus, SDIO, UART 1, I2C1 & USB Host

Or something similar for an Alloy MicroMod replacing the STM with ESP
For BlackEdge the pins would need a rewrite, even then there may be too few..

[Folknology]

I think Sparkfun's 2 biggest mistakes with their pinouts (ignoring the weirdness of not following the E Key Spec) :

1. The AX,DX and PWMX should all just be MX pins (6 analog/digital pins)
2. The GX/Bus pins should be hi speed digital only (no analog)

Actually there is one other super fuckup and that is not supporting JTAG as well as SWD it would only require some pin doubling up, they could prob change that

[Folknology]

One other limitation that I have been thinking about with regard to the MicroMod 'standard'.

The standard assumes a 22x22mm board with specific fastening making both ends of the board unavailable for mounting high speed connector directly on the module (where you need them), this was an important design feature required for BlackEdge. Thus if you want to support HDMI, USB3, MIPI CSI etc you are out of luck. With BlackEdge we anticipated mounting these on the core board directly using industry standard connectors where possible, clearly this has not been considered in MicroMod's standard..

[lawrie]

@Folknology Have you looked at the SYZYGY connector - see https://groupgets.com/campaigns/868-butterstick

[Folknology]

It's quite tricky both for the carrier and peripheral, not sure about pricing?

I would like to know more, anyone tried these?

[Folknology]

Some detail about SYZYGY re FPGA IO