What are they designed to do, and what are the software interfaces?
LED11 = AXP209.gpio3
LED10 = AXP209.gpio2 (status indicator of CPU boot by default)
CHGLED = AXP209.CHG LED (indicating LiPo charge if it would used, but as it also introduces noise to the system we eliminated LiPo powering option)
Misc items / Headers
- two pin header between power buttons marked “2 1” Possibly LIPO_BAT? Battery backup? battery power?
Lipo battery input, not used only for evaluation reasons.
- Switch between the power buttons, marked
connected to A13.PD3 gpio, customer can use this if want
---- Auto Boot (auto boot on power up?)
Auto Boot is not yet implement in FW, coming soon.
This connected to A13.PD2 gpio
- Two pin header marked CHG_IN
“ACIN” alternative power input power of AXP209, not functional now, only the USB power input powering the whole circuitry now for keeping the switching regulator noise down. (Low noise operation was the highest priority due the sensitive SDR / LNA parts.)
Current sensing jumper on the micro USB 5V input port. One can cut the copper trace between the two pins with x-acto knife and be able to measure current with a multi meter on those points.
Main header pins
Can you define what these pins are for? of course some are obvious, but please confirm and state if there are other purposes for them. if there is a /sys/class for export or /dev use what is that?
5V0 5.0 Volt (max current?)
About 100mA is a safe limit. it’s tied to a DCDC step up regulator not the 5V USB source (this will changed in later release some)
3V3 3.3Volt (max current?)
About 100mA is a safe limit.
These are simply the GPIO ports of the A13 SoC, check the datasheet for more information.
Some example on GPIO usage: https://docs.outernet.is/Dreamcatcher%20Armbian%20Code%20Snippets.html