Last week we are focus on the mass production.
From the beta production, we found some problems and that might lead to big problems in mass production.
1. Some parts in BOM are changed.
The factory engineer said they changed the BOM parts by their exists parts. That is a default rule, so they did not notice me that.
Before production, we found the flash chip was changed from W25Q64FVTIM to W25Q64FVSSIG. There are two kinds of alpha board, 200pcs are using W25Q64FVTIM, and 100pcs are using W25Q64FVSSIG. W25Q64FVTIM is 1mm tall, same as SDRAM, W25Q64FVSSIG is 2.3mm tall. W25Q64FVTIM cost is 30% higher than W25Q64FVSSIG and it is rare in market. W25Q64FVTIM is the only prefect one due to its small size and later hobbyists can easily hack it to other SOIC8 chip(VSOP8 is compatible with SOIC8).
PS: current mass production buy out all exists W25Q64FVTIM in ShenZhen electronics market. 😀
When I get the demo board, I found the power inductance is changed from LQH2HPN2R2MJ0L to SWPA252010S2R2MT(final version it is SWPA252012S3R3MT). From datasheet, Sunlord one have better performance in higher current(>600mA) but its resistance is 0.21ohm compared Murata one is 0.14ohm. So that might make the power consume a little higher, about 0.015w. This is not prefect, but acceptable due to better performance.
2. Test process.
They are using QA tool for mass production quality test, that tool is mainly used for router and phone(that factory is big, main job is to make router/phone parts for Samsung and TP-LINK) but never did such develop board for hobbyist. OpenWrt wifi driver do not support QA tool due to it do not have RT5350 native io control. I want VoCore to have a prefect quality, so it must use the QA tool. We use RT5350 SDK to run QA then flash it to openwrt for other tests. That process is complex and the factory is unhappy, I have to code a helper application(auto test from telnet/serial), also this app helps the factory to test their other production, so they are happy after that, and no manual operation also helps VoCore avoid test mistakes.
There are thousands of packages contains different perks. That is a big work. I write a small application to filter the packages, about 2200+ packages are normal, but hundreds of packages are incorrect. Some only have Dock but no VoCore, some addresses are not right, have to email them later and deal manually. If I have next crowd-funding campaign, I will make the perks as simple as possible.