Data Bus Routing
Well, seems it’s easier said then done. For the last week I’ve been trying to route my data bus (highlighted in the picture) to the FPGA (the left most IC). Considering I’m trying to do it on a two layer board I have no idea how I’ll do it. Feel free to leave a suggestion. Other possibilities include making a daughterboard with the ARM9 and memory. That would “Emulate” a 4 layer PCB and would allow me to reuse the “core” module.
18 bit address bus routed to FPGA
A milestone was reached today, I’ve routed the 18bit address bus to the FPGA, next is the 32bit data bus. Click image for PCB fun.
Dual Layer AT91SAM9260 Board
Up until now I limited my self to text VFDs or LCDs with a common HD44780 interface but yesterday, I stumbled upon this nice PSP-LCD (LQ043T3DX02) for sell on SparkFun. Now I wanted to do graphics ! However you won’t display something on those LCDs with a PIC16F… (Well maybe a dual port memory with a CPLD to do the timings)
As my projects (Blamp and my active speakers) progress, I always find myself in need of a fast core with possibility of lots of expansion and that can be deeply embedded (read: no ports on the board). Here enters my efforts to have a working, dual-layer AT91SAM960 board with 256Mb RAM and a FPGA. oh and yes, it will run Linux.
Three Way Active Speaker
There comes a time when you just want to build the whole thing. I recently read about a DIYer who built a three way enclosures with Vifa Drivers. For space saving it would be the perfect enclosures to build the amplifier in it. Since Adam McCall got beautiful results I decided not to reinvent the wheel and build from his plans.
But why just one amplifier ?
Active Crossover, Class-A 20w Tweeter Amp, Class-AB 50w Full Midrange Amp, Class D 200w Woofer Amp.
Stay Tuned
The Pre-Amp Chain
As you may or may not know I’m building an audio/video pre-amplifier/pre-processor. Since this a quite a bit DIY project I decided to make it very modular.
It will accept either SPDI/F coax and optical as input along with the more basic analog inputs. Every input module handle one input and will output an I2S signal over a 5 pin header (4 for I2S and the last bit will be for if audio is present). Every input will then go to a mux board which will simply be relays controlled by the main logic board (possibly by some simple PIC) this board will have only one output and will be I2S. Exception to this will be the SPDI/F inputs; the CS8416 in software mode will be responsible for the mux and the output will then go to the mux board.
The fun stuff will be on the main board; the I2S input will go into a SRC (Sample Rate Conversion) the output will always be at 24-bit 192kHz and will go into a DSP. The SRC will be pulled into bypass if the “audio present” bit is not present – this will allow me to pass raw SPDI/F data and possibly implement AC-3. The main control logic will be a Freescale Coldfire MCF5282 at 80Mhz and will possibly interface with a Freescale DSP56367. The Coldfire will handle the infrared, the VFD display the power (ON/OFF), programming the DSP and monitoring the pre-amp for over-temp and such.
The video will follow the same pattern; Inputs will be converted to digital, will be muxed and then back to analog for the output – however I will not put a DSP in the single path. This project is already complex as it is.
For the power I decided to keep it simple and will use a ATX12v power supply.
Right now, the output PCB is done and I’m designing the main board. Fun stuff !
40w Class-A PCB Power Amp
Version 2
Features more space and place for bigger heatsinks. I also added a balanced input driver (INA137 at -6dB)
Differential Output Stage
It’s one thing to build and amplifier, it’s another to build a pre-amplifier. I selected a CS4398 [PDF] as DAC; this chip has a differential output for both channels, an I2S input and up to 120dB dynamic range.
What’s nice is that Cirrus Logic made a very well designed evaluation board for this chip, the CS4398. I’ve used the XLR output as a starting point for my own output stage.
The DAC will run at 96kHz with an oversample of 512x. The master clock is just over 49MHz (49.1520MHz). The input (I2S) will be feed from either a DSP or my “Core Module”; I have not yet tested if the ColdFire v2 @ 66MHz will be able to keep up with video & audio. As for the PCB, all the components will be surface mount to minimize space and keep the trace length to a minimum.
JLH Amp PCB
Well I just finished my PCB layout for one of my class A power amplifier;
I will now attack the blanced input stage. I was thinking about a simple op-amp with a buffer right before the “input”.
Why sit and watch
More people watch and vote for American Idol then the presidential elections. Why are we sitting and watching ?
Furiously dialing, spending money on this staged democracy, for the next diva of music; at least for a handful of years. For a moment it creates life on our couches; a temporary expression of vitality. Our desire to see one hero, beaten, stabbed to death, triumph leaving a trail of destruction behind is, perhaps, the only emotion that allows us to delay the unthinkable while we wait on our couches to die.
To have one’s birth certificate expire one has to have one. Is it still possible to think about yourself ? If one think, since one think one is, what happens when one is unwilling to stop and think ?