Monthly Archives: June 2014

VoCore Alpha Fix Video

Here is the video:

This is only for alpha, release version do not need such fix 🙂
Thanks for my teammate WuTong, this video looks so professional. And special thanks for my friend Alex helped to make this video.

Some notes from WuTong:

1. Better to have a tip iron, that will help a lot.

2. Better to have this tool to keep it in position.

3. Better to have a light.

PS: in the package there are are some resistors, four 154Kohm and four 158ohm, those are useless now, just ignore them.

VoCore Alpha Usage

From the China Post, I have get all trace id, the track id will be updated to my server tomorrow, you can get it through that stupid robot 😀[Your Invoice ID],[Your Email]. For alpha users only.

PS: Next week I will update that stupid robot, add all user data to it and you can easily change your information online. The China Post request me the phone number, but indiegogo do not have that.

You will never know that robot is written in pure C 😀 I am not good at PHP or other web language yet.

Now the USAGE of VoCore Alpha:

(MUST fix the board first, please check for the fix)



Do you find that two red box? Connect power to it, any power between 3.3V~6.0V is OK(USB, Li Battery, etc…)

Once connect to power, the LED will light about 1sec, that means VoCore is on boot. Wait about 30 seconds, you will find a AP named VoCore, connect to it.





  • LuCI Login:

Now please open your browser, visit VoCore root site,, default username is root, default password is vocore.



Now everything is ready for UI login.


  • SSH Login

open command ui or windows could use putty.

ssh root@

Type ‘yes’ then return/enter when it request.
Input password ‘vocore’, then you are in openwrt. 😀

Screen Shot 2014-06-25 at 15.55.41


OK, that is all.

When I get it work, I make it into AP+STA mode at first 😀 This blog is send though my VoCore AP+STA mode(

Alpha version do not have MAC address yet, all of them are using same MAC, but release version will have.


VoCore Hardware: How to Fix Alpha

First: this one is fixed one:


Plan A: Simple Tools(need high skill):

Step 1 => take off the old 27pF cap.

I am using Ag-Sn, 221C melt down(Ag-Sn-Cu is another choice). And 180C Pb-Sn or Ag-Bi-Sn should be OK too.

Use the tweezer bit that 27pF cap, then use your iron(better to be 280~300C) touch the one red point, about 1 second, move to another red point for 1 second, do this again and again… until the paste is melted.(my iron is not good, only 250C, it takes about 2min) Then your tweezer will get the cap.


Step 2 => solder 27pF cap onto the position.

We need to cut off some Ag-Sn from the Ag-Sn bunch.
Use iron to melt them into two about 0.3mm Ag-Sn metal ball.
The ball can not be too big, or it will be easy to cause short connect, and once it is short connected, it is very hard to fix.


There are two white point.
Put a little flux onto the white cycle, the put one little Ag-Sn ball to one white cycle(the flux is used to keep the ball touch the PCB and not roll to everywhere.)
Put the 0402 cap beside that ball. Like this:

Use your iron melt that ball, so one side of the 27pF is connected to 300ohm(or 1uF)

Then put other ball between another white cycle and another side of 27pF, use the iron melt down that ball. Now the 27pF should be well connected with the two white point.

Plan B: Hot air + Ag-Sn-Cu Paste(about 226C) (very easy)


Step 1 => Make hot air to 280C~300C, target to that 27pF, about 30second, use tweezer take it off.

Step 2 => Put 27pF onto the position(blue rectangle).

Use your tweezer get a little paste, and put some to the white cycle.(do not put too much or it will short connected). Then put 27pF on the paste.

Hot air again, melt down that paste, it is connect perfectly.

VoCore: Alpha Version 5



An ugly fix from me 🙂

PS: If you have additional 0402 27pF(> 6.3V, 10%), solder it to the position should be OK too, do not have to move/remove the old 27pF.

VoCore: Alpha Version 4

The six days I checked many possibilities…
Finally, I find it is clock circuit problem.

This is clock sch from v0.5:



This is clock sch from v1.0a:



So do you find the problem?

I moved 27pF cap to other side of the crystal for the new version…I did not even notice that …(when I optimised the layout of the PCB, I changed some parts of schematic, then forgot to change this part back…)

This small careless problem caused the hole board unstable and the wifi not working. Such problem will never happen again.


Why this BUG is so critical?

Normally, hardware is stable and able to afford some problem, for example, if you remove two or three 0.1uF cap, it works normal.

But crystal problem is always a big problem.

If RT5350 is the heart of VoCore, the crystal(clock) is the heart of RT5350. It can not work with a buggy clock.

v0.5 circuit is a standard noise reduction circuit, the high frequent noises are block by the 300ohm, and direct to ground by the 27pF cap. But when I move 27pF cap to another side, this RC noise reduction circuit is broken, so clock noise will be very loud, so some chips are unstable. Wifi signal is 2.4GHz, that is from crystal clock(20MHz) x 120, the noise is even 120 times stronger than the chip, so the wifi is not working at all.

This morning I contact the factory, their repair team is very busy, we have to wait at least one week. And from WuTong, The alpha VoCores had shipped to China Post and I can not make them back to change any hardware, so the alpha contributor have to change this yourself. Really sorry for that problem, I will record a video or write a blog with detail to show how to make that.

For simple, it should be changed like this:

VoCore: Alpha Version 3

Good news 🙂
Finally I find the real problem…Thank you for everyone help!!!
I have fixed three boards, so I think 99% chance I get this bug.
It is very late day, I will public it tomorrow afternoon. Keep that as a secret for couple hours. 😀

And tomorrow daylight I need to contact the factory first, ask if they can fix the 300 pcs for me. If not, that will be a little trick for new hand of iron/hot air gun.

This indiegogo campaign makes me carries too much…For 2K more contributors, I can not afford any mistake. After this I will/must have a big rest. 😀 😀 😀

VoCore: Alpha Version 2


after I changed the power input to 3.2V, it works stable over 24 hours, during the time, I tested GPIO, works well. Wifi has signal and it is fair, but I can not connect to it from computer, just get some weird system log, looks like the hardware of wifi still have some problem.

root@OpenWrt:/# logread -f
Sat Jun 14 20:16:02 2014 hostapd: wlan0: STA b8:f6:b2:1a:7b:ed IEEE 802.11: authenticated
Sat Jun 14 20:16:02 2014 hostapd: wlan0: STA b8:f6:b2:1a:7b:ed IEEE 802.11: associated (aid 1)
Sat Jun 14 20:16:02 2014 dnsmasq-dhcp[881]: DHCPREQUEST(br-lan) b8:f6:b2:1a:7b:ed 
Sat Jun 14 20:16:02 2014 dnsmasq-dhcp[881]: DHCPACK(br-lan) b8:f6:b2:1a:7b:ed Vongers-MBP
Sat Jun 14 20:16:03 2014 dnsmasq-dhcp[881]: DHCPREQUEST(br-lan) b8:f6:b2:1a:7b:ed 
Sat Jun 14 20:16:03 2014 dnsmasq-dhcp[881]: DHCPACK(br-lan) b8:f6:b2:1a:7b:ed Vongers-MBP
Sat Jun 14 20:16:06 2014 dnsmasq-dhcp[881]: DHCPREQUEST(br-lan) b8:f6:b2:1a:7b:ed 
Sat Jun 14 20:16:06 2014 dnsmasq-dhcp[881]: DHCPACK(br-lan) b8:f6:b2:1a:7b:ed Vongers-MBP
Sat Jun 14 20:16:10 2014 dnsmasq-dhcp[881]: DHCPDISCOVER(br-lan) b8:f6:b2:1a:7b:ed 
Sat Jun 14 20:16:10 2014 dnsmasq-dhcp[881]: DHCPOFFER(br-lan) b8:f6:b2:1a:7b:ed 
Sat Jun 14 20:16:12 2014 dnsmasq-dhcp[881]: DHCPDISCOVER(br-lan) b8:f6:b2:1a:7b:ed 
Sat Jun 14 20:16:12 2014 dnsmasq-dhcp[881]: DHCPOFFER(br-lan) b8:f6:b2:1a:7b:ed 
Sat Jun 14 20:16:14 2014 dnsmasq-dhcp[881]: DHCPDISCOVER(br-lan) b8:f6:b2:1a:7b:ed 
Sat Jun 14 20:16:14 2014 dnsmasq-dhcp[881]: DHCPOFFER(br-lan) b8:f6:b2:1a:7b:ed 
Sat Jun 14 20:16:15 2014 hostapd: wlan0: STA b8:f6:b2:1a:7b:ed IEEE 802.11: disassociated
Sat Jun 14 20:16:16 2014 hostapd: wlan0: STA b8:f6:b2:1a:7b:ed IEEE 802.11: deauthenticated due to inactivity (timer DEAUTH/REMOVE)

Some boards(about 40%) are not stable, I add 0402 154Kohm 1% and 0402 158Kohm 1% resistor to the package, so if your alpha board can not work well(boot up with system oops), please replace the 150Kohm on board to 154Kohm or 158Kohm, this is a dirty fix before we find the real problem.

And further alpha test/fix report I will public in the forum but not blog, that will be easier for us to discuss the problem. 🙂

Finger cross, hope I find the wifi problem soon…

VoCore: Alpha Version

Get the 300 pieces from factory:

The alpha version have tons of bugs, be happy to catch them 😀

From my first test, there are two main problems:

1. the board is not stable through 3.3V~6V port, many oops when system boot up, but through 3.3V pin(input set to 3.1V~3.2V), the system works normal.

2. From computer/phone we are able to find VoCore wifi hotpot, but after connect to it, it shows a warning, can not ssh to the board. error

First problem, I think it is PCB problem or design problem. But the design is copied from v0.5(some wire changed, I must compare them. Never be too careful, specially on hardware), and v0.5 is normal. So high chance to be PCB problem. Might be crosstalk? From my simulation the max crosstalk is 84mV(3.0V, 1.0ns), in most situation the max allowed value should be 150mV.

Second problem, just no idea, might caused by first problem. Same firmware works well on v0.5 but not this one.

From the factory engineer, he said two points must be improved in next PCB version:

1. V-CUT border is too closed to each other, some pin hole might be broken after SMT.
2. V-CUT is not good for such small board, the copper is easy to be stretched when they cut it into pieces, so it will effect signal.

I thought there might be some small problem such as wifi signal in the alpha version but I never thought these problems are so big…None of that happens to my test version v0.3 or v0.5.

I am really sorry, I planed this version should be at least as good as v0.5… I will also ship a small gift to all the alpha tester(USB<=>TTL/UART device), hope your testers will be a little happier. 🙂

And the boards will be shipped in this week. I am so limited, please help me make it better, really appreciate!

The Four Days

It is a long time 🙂 Now I am able to upload something to my blog.
Jun.09, at ShenZhen.

Jun.10, shopping.(forget to take picture…)

Jun.11, factory.

It is much faster than my hand solder. 😀 VoCore alpha is only 300 pieces, so they plan to make them about Jun.12 night in three hours.

What is this? 🙂

And special thanks for ShenZhen TechSpace or I will have no chance to meet so many creativity people there.