In another thread (Divorce from Adapters: Taking the Custom "Block" Plunge), I alluded to this question, but let me say ask it directly here. I want to see if I can understand the minimum requirements to get Edison to boot without either of the breakout boards. The question is:
- What is the minimal set of buses/signals that need to be manipulated to get Edison to boot from a 3.7V LiPo battery?
Power rails
Obviously, we need to connect the positive battery terminal to VSYS and the negative to GND.
PWRBTN#?
It's been recommended that we strap PWRBTN# to VSYS with a 10K resistor. (Both the mini breakout and the SparkFun console block do this.)
DCIN?
The breakout guide says
- DCIN is a signal that indicates whether Edison is being powered from a battery or from an external power source. DCIN also sets the voltage level required on VSYS in order to boot. When DCIN is floating or tied to ground, the voltage on VSYS must rise from 2.5 to 3.5 V in 10 ms; otherwise the boot is aborted. When the boot is aborted, power must be cycled below 2.5 V. If DCIN is connected to VSYS, Edison will start to boot when VSYS is above 2.5 V for 100 ms.
- Note: When DCIN is connected to VSYS, boot will occur whenever the voltage is above 2.8 V for 100 ms. The DCIN signal is attached to VSYS on the PCB.
I can't quite parse this. How exactly does one tell the Edison that it's powered from battery? Also it would seem that the "Note" completely overrides the bold sentence immediately prior. What do we need to do with this DCIN signal? Is this relevant to applications that don't use the breakouts?
RESETOUT#?
The mini-breakout board straps this to 1.8V via a 10K resistor, but I think this is just for the green "all's well" LED. Do we have to do anything with this signal?
Other?
Thank you,
Mikal Hart