迷你部落格

Long day for me to update my blog. I even don't know my blog was blocked by our Great Fire Wall.

Yesterday I passed my first time of GRE test. That's a f**k test. But during the day of preparing the GRE, I got a chance to attend our University's electronic design contest. In the contest, I fixed some problems of my power and add some now function into it.

This is the top layer of the power. You can see a black PCB which plug into the main board. That's a current detection module. I using TI's INA200A to detecting the current of power's output. Then using Arduino's ADC to check out the current if the current exceeds the threshold value. This threshold value could change during the runtime. If the power is overloaded, the relay (yellow thing) will cut off the output to protect the buck chip until manual reset the system.

The 1602 LCD could display the output voltage, output current and cut off thrshold current value. Using Arduino to control the LCD is very simple like using printf() function in C language.

This the bottom layer of the power. I using the surface mount package part to keep the system small.

This is the out put waveforms. About 15mV ripple voltage in 1A load, 10V output. Fantastic result by using Nichicon HD aluminium electrolytic capacitor.

That's all of the
This project is open-sourced, under the licence of BY-NC-SA. If you want the SCH, PCB file and Arduino file, leave the comment and I will mail you ASAP.
Thanks to Texas Instruments for offering me so many kind of chips free.

We use TI's TLC5615, 10-BIT DIGITAL-TO-ANALOG CONVERTERS as our DAC.
This chip has 3-Wire Serial Interface, so we can use Arduino to control it.
Arduino is an open-source physical computing platform based on the AVR MCU.
Now give the Arduino program.

//Arduino project http://arduino.cc
//by Mini Dragon at http://minidr.com/archives/687
//This program is licensed under a Creative Commons Attribution-ShareAlike 3.0 License.
#define CS 2 //chip enable
#define CLOCK 3
#define DATA  4
 
#define HALF_CLOCK_PERIOD 2 //2 uS of clock period 
float j=0;
void setup()
{
	pinMode(DATA, OUTPUT);
	pinMode(CLOCK,OUTPUT);
	pinMode(CS,OUTPUT);
	digitalWrite(CS,HIGH);
	digitalWrite(DATA,LOW);
	digitalWrite(CLOCK,LOW); 
}
 
void writeValue(uint16_t value)
{
	digitalWrite(CS,LOW);//start of 12 bit data sequence
	digitalWrite(CLOCK,LOW);
	data = data << 2; //Add 2 0 at the end of the data. A 10-bit data word should add 2 0 at the LSB bit (sub-LSB) since the DAC input latch is 12 bits wide.(SEE TLC5615C DATASHEET) 	
	for(int i=11; i>=0; i--)//send the 12 bit sample data
	{
		digitalWrite(DATA, (value & (1 << i) ) >> i );//DATA ready
		delayMicroseconds(HALF_CLOCK_PERIOD);
		digitalWrite(CLOCK,HIGH);//DAC get DATA at positive edge
		delayMicroseconds(HALF_CLOCK_PERIOD);
		digitalWrite(CLOCK,LOW);
	}
	digitalWrite(CS,HIGH);//end 12 bit data sequence
}
 
void loop()
{
	j=567; //in here, 567 is a example. DAC OUT=j*Vref/1024
	writeValue(floor(j));
}

Each DAC output voltage maps a main Vout.
To be continued.

[Update 2014/Tue/22] Code Opt

我使用乐之邦轩辕五周年限量纪念版也有1年了,首先不得不承认,音质比AC97那种集成垃圾声卡好多了.独立声卡的声音就像眼前一亮,穿云拨日的感觉,音乐层次相当分明,就是拉拉那种多媒体音箱,效果也好多了.

在我的眼中,声卡分三类.能放出声音的,代替集成声卡;消费级声卡,有韵味了;专业级声卡,价格不是一般人能接受的.我用的就是消费级的.下面介绍一下.

1.主控芯片是VIA TREMOR系列的VT1721,支持24Bit/192kHz的数字信号.这个芯片是172X中最高级的.而VT家族是独立消费级声卡中最常见的.普通的集成声卡一般都只支持到48kHz.独立声卡分辨率上去了,音质更加好了.

2.Wolfson WM8776 高精度编解码器(DAC),108dB的模拟播放和102dB的模拟录音.信噪比上去了,音质会不好吗?这个牌子还是iPod用的解码器,也算消费级大军了.

3.每声道独立运放OP275,双级型与JFET型混合结构,运放的好处就是驱动功能更加强了,能驱动中,低阻抗耳机了,推推DJ耳机也不费力了.让集成声卡推大耳机就是软绵绵,集成声卡芯片直接输出电流不够啊,加了运放,甚至能对地短路呢.不相信看PDF.

4.晶振由原来的24.576MHz晶体升级成49.152MHz.这个就是192kHz用的.

5.电源滤波电容由原来的NCC的LXY系列升级到NCC的KEZ超低阻抗,高频滤波专用电容,提供更纯净的电源供应.还有3路电源供应.一组7805给VT1721主控,ATMEL的ROM供电,一组7805给WM8776解码器供电,一组7805,7905给前级放大电路供电.这个专用滤波电容和线性稳压模块是集成声卡,也就是主板厂商不敢考虑的,体积和成本的问题.我记得捷波出过一个带运放的主板,用了两个大大的固态电容,运放还是能拆卸更换的,各大媒体就大肆报道.创新啊什么的.

6.前级音频电路中,原来的NCC LXY系列电容换成nichicon FW系列音响电容.

7.前级音频电路中,原来的红WIMA电容升级到黑WIMA MKS2系列电容音响电容,声音更富有音乐味.

8.提供低延时的ASIO播放,录音.和其他支持ASIO驱动的主控芯片一样,ASIO模式能绕开Windows底层驱动,直接输出到声卡,降低延迟.ASIO模式下,只允许一个程序发声,并且Windows的音量调节模块对ASIO程序无效.目前,Adobe Audition,Apple Logic Stdio都支持ASIO模块了.

9. 高性能光纤,同轴输出,支持2声道PCM和Dolby,DTS等多声道码流输出,数字输出增加Dolby Digital Live.这个我接外部功放的时候,不同码流功放的灯都是不一样的,很牛X.

本人还花了点钱对这张卡进行了打磨.也就是换电容.都用Nichikon了,干嘛不再用得好点呢?板子上一共有5个Nichicon FW系列的音箱电容,输出两个,输入两个,话筒1个,全部换掉,换成更高级的Nichicon ES系列Muse无极性电容,这款电容是专门用来级间耦合的无极性电容,Muse是宙斯的女儿,专管文艺,所以代表了Nichicon电容中最高水品,音质更加纯净.运放我就不换了.运放换不好声音听起来会很怪.一般厂家出厂用的都是比较均衡的,自己换了后可能会出现某些频段的缺失,还不如不换.这是我换过运放后的感触,只要解析度够好,味道适中就行了,什么胆味不胆味,不是每个人都能适应的.

我玩音响也挺久了,现在的装备是这个声卡数字输出到安桥功放再到天朗705.好的音箱听多了,也造就了我的金耳朵.我已经不屑听垃圾音箱了.

注意:Nichicon是日货,抵制日货请绕道.