HackRF
23.11 Shield Support
If support for add-on shields is considered valuable, here are some tweaks I’d suggest:
Any reason P28 (SD) pin 12 isn’t grounded or doing something useful? Same goes for P25 (LPC_ISP) pin 3 – maybe
make it VCC, the signaling voltage for the ISP interface? The SPIFI connector could also use a reference voltage
(GND?).
I’d like to see an I2C bus exposed somewhere, and perhaps an I2S0_RX_SDA signal, so I don’t have to steal it from
the CPLD interface. The I2S0 will function in “four-wire mode” with only one more pin (RX_SDA), so why not?
Provide a way to inject a supply voltage into the board? Having diodes managing multiple voltage sources would be
lossy, so a more expensive solution would be necessary on the Jawbreaker board, adding cost.
If an LPC43xx package with a higher pin-count is used, it would be stellar to expose the LCD interface and quadrature
encoder peripheral pins.
The RTC would be handy for stand-alone use. This would require a crystal (32.768kHz) between RTCX1 and RTCX2,
and exposing VBAT to a shield for battery backup (disconnecting it from VCC) or providing a coin cell footprint on
the HackRF PCB.
Coalesce separate headers into fewer, larger banks of headers, to reduce the number of unique, small header receptacles
required for mating? Reducing the header count will also increase the amount of board space around the perimeter of
a shield for components and connectors.
23.11. Shield Support 87
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