Hardware questions about A64-OLinuXino-1Ge16GW-EA board

[nlc]

Hello, for a new project I need to choose an SBC, and A64-OLinuXino-1Ge16GW-EA can be the perfect choice. But I need some confirmations :

- I need RTC and RTC backup to keep time during power off periods. The board description says : "RTC battery expansion: pad provided for powering the RTC of AXP803".
But I looked the schematic, the AXP803 VCC_RTC is an always enabled supply output. I am not sure it's a good idea to connect a 3V coin cell (3.0V_RTC1 soldering pad) on this output ? The AXP803 doesn't include a RTC, I suppose it's a mistake in the description and the RTC is managed by the A64, because the 32kHz crystal is connect to the A64.
Can you confirm the RTC is working on this board ?

- I need a free SPI bus to connect a external 24bits ADC, on the UEXT1 connector, SPI is available, but can you confirm it is free for user, even on the eMMC version of the board ?

- I need an uart to communicate with an external display. I can use the  serial UART debug header for this purpose but I would prefer to keep it for debug and Linux console. Is there at least another free uart available on GPIO expansion header ?

- I need some GPIO for input/output, and ideally 4 PWM outputs, but it seems the A64 has only one PWM channel ?

Regards,
Cyril

[LubOlimex]

Overall I think the A64 board would fit your project.

The description is correct you can solder 3V battery to the pads and have the RTC backed up.

You have free SPI and free UART and free GPIOs, no worries.

A64 has less than 4 PWMs for sure, and it is uncommon for similar Linux chips to have more than two PWMs. But you can expands the design with external PWM expander board over common interface like I2C.