The TempoAutomation team that want’s to build a DIY minifab for electronic circuits has a prototype pick-and-place machine running. It looks like they’re using a Makerbot as the base. There is one problem with this approach: the Makerbot mechanic is not designed for high positioning speed. Using a larger CNC mill could improve speed a lot. But this is only a development prototype, we might see big improvements in the future. Having a machine that could place solder paste and components on the board would be cool.
After some hours of debugging and fixing a hardware problem, the DSP hardware seems to work now.
There are still cables soldered for I2C debugging purposes, but writing to the DSP works without problems now. I still have to work on reading data back from the DSP. Therefore the debug cables are still soldered. You also see, that the voltage regulator at the bottom is not used yet. I will do some comparison tests with a separate voltage regulator for the analog circuit.
I created a simple DSP program that generated different waveforms on the different output. Let’s see what happens on the output:
Looks good! The DSP now runs at 48kHz, therefore the triangle waveform is not exactly a triangle. But that’s what you would expect.
Many PCBs have a large ground plane where most components connect to. In simple microcontroller circuits, this usually works well. But for complex and mixed analog/digital circuits, you need to think a bit more how to route your ground traces. If you want to design your own PCB, have a look at this tutorial document from Analog Devices.
Just a quick update: I did the first tests with HiFiBerry Mini – our high-resolution DAC for the Raspberry Pi. The card is working, sine waves look great on the oscilloscope. More tests have to be done. I will be interesting to see what will be the highest sample rate that I get running on the Raspberry – the DAC supports up to 384kHz!
And there is the next Raspberry sound project – the HifiBerry Mini. This is a DAC for the Raspberry Pi, that is based on a PCM5102 from Texas Instruments. It has a The chip runs at 3.3V and used the 3.3V provided by the Raspberry Pi. Because this supply is quite noisy, it will be used only for the digital part of the chip. The analog output will be sourced by the TPS7A4901 – also from Texas Instruments. This is a high-end voltage regulator specifically designed for ultra-low-noise analog circuits.
This PCB is also a good device to practice SMD soldering. Both ICs comes in 0.65mm pin pitch. Almost all passive components are 0603 packages. But don’t be scared! You only need some magnifying glasses (I use 2.5x magnification), a good soldering iron and good solder paste (this is really important!). If you don’t believe me, check out the soldering tutorials that I linked here. There is no need for a reflow oven for this circuit.
Unfortunately all passive components are missing at the moment. They should arrive in the next days. Then I will be able to test the device. Stay tuned!
This is only a preview, the design is not finished yet.
The HifiBerry USB prototype is almost finished. Soldering the small TSSOP package of the sound chip is not trivial, but still possible with a good soldering iron, some solder wick and a magnifying glass. Unfortunately, I forgot to order the 12k resistor for the voltage regulator. For the tests, a combination of 10k and 2k in series will do the job.
First measurements look ok, all voltages are good, current drawn without USB connection is 12 mA and the oscillator is working. Therefore I think, that there are no major problems. Without USB connection, the onboard voltage regulator for the analog stage is disabled, therefore I couldn’t test it yet. Stay tuned for more information.
I agree, that there are a lot of Raspberry Pi related postings in the last time, that do not look like audio related postings. But I can tell you – they are. We’re working on audio projects for the Raspberry Pi. The goal is to have a high quality sound system based on a Raspberry Pi. One thing, that we could not find somewhere, was a simple template for a Raspberry Pi extension board. Therefore we created one. The board size is the same 85x56mm as the Raspberry Pi itself and it includes the extension headers P1 and P5. P5 is especially important for audio, because that’s the I2S header. The template is available freely on Github.