I'm building a base for future projects. Why would you design this thing?
- Learning experience
- Fun?
The hardware will be in different layers/floors/segments... That will add certain functionality depending on the project.
At the moment, I'm designing the main part of the tower. Which will be based around the Rockchip RK3308B.
Before this, I've tried working with a SoM of imx6ull and stm32mp153. Although I managed to get to a working system, I just wasn't happy with the result.
The move to RK3308B has some pros and cons:
Pros
- Low idle power consumption 260mW (based of long term measurement of Raxda Rock S0 running kernel 6.1 debian bookworm, wifi listening)
- Move from armhf to aarch64, mainly because I use java for my other project and new jre's aren't build anymore for armhf.
- 'Entry level' SoC, so messing things up doesn't hurt as much (€) as with a SoM.
- Used by Raxda Rock pi S(0), Banana Pi BPI P2 ... so working kernel/rootfs etc should be easy to obtain
Cons
- Learning yet another environment (iMX->STM32MP1->Rockchip)
- Not starting from a SoM means the design is a lot harder, will be my first time working with BGA, DDR Ram etc.
- Documentation isn't easy to come by. Won't share them in the repo because some had 'confidantial' stamped over them.
- Took me some time to find the datasheet for the RK3308B and that's for version 1.2 eventhough 1.3 is out. The RK3308 can be found on the official site.
- Found the TRM for the RK3308 but unsure if 1.1 is latest version.
- Haven't found an official reference design/guides, so based it off the the earlier mentioned Raxda rock s0.
- 0.65mm pitch BGA
Started the design, currently on a four layer PCB.
- All basics are in the schematic (ram,emmc,phy,buck,usd)
- Layout of most is done (ddr was fun)
With starting from scratch come a lot more choices with regards to components used.
- 512MB DDR3L Ram
- 16GB eMMC HS200, 8GB or lower isn't worth the price difference (1€ difference at the moment)
- Discrete power supplies: Buck TPS62A0x and LDO TLV755
- Probably try a PMIC for rev 1, but keeping things 'simple' for now.
- 10/100Mbps Ethernet PHY LAN8720A