OP here, please forgive my absence, lots of work during the last months, won't get better soon.
TinyTOSLINK started a lot more tiny, for the rev. B board. That's why it is reduced to the minimum component count. No space for series resistors.
http://www.raspberrypi.org/forums/viewt ... 45&t=75225
However, I always had an L/C-filter for the PLL supply, pin 7 PVDD, and a very good clock crystal.
(Later version has 5 extra components for the galvanic S/PDIF out/in.)
The B+ board in comparison is rather spacious. I even was experimenting with small pulse transformers for insulated S/PDIF.
The PLT133/T8 transmitter with the shutter mechanism is kind of tall. It will reach all the way down touching the activity LEDs, perhaps colliding with cabinet lightguards. If anybody wants some, I have a dozen of them left, consider them a mis-buy.
I chose a different part, DLT2153A from Aixin. Very low profile, no shutter, comes with a plug. Extra benefit is that the Aixin transmitters are the rare kind reaching 25 MHz, which is needed for 192kHz/24bit audio. (If the receiver is the same grade.) Really works, I can confirm.
Hard to get, my source only was an AliExpress shop from the manufacturer. Only worth if buying a lot, since they charge about $40 for shipment.
Ben, do you allow some constructive criticism and questions about your board? I'd like to mention:
- Why such big resistors? 0603 would fit be the design well, since Eagle footprints are on the large side anyway, 0805 can be used even on 0603 footprint.
- In contrast, the crystal is really tiny. You should ground the remaining 2 pins, they are connected to the case shield.
- Power traces could be thicker. I hope you have a ground polygon. I've avoided long traces on the bottom side, mine is basically a ground plane, with only a few short traces crossing.
- The split connector makes it difficult to properly align the halves. (They even have different pin counts?) Eagle has huge holes for headers, so they have a lot of play. At least, plug them on the RasPi connector before soldering in, to help alignment.
- Better ground the write-protect line (pin 5) of the EEPROM.
- No need for pullup/down resistors on pin 2 and 5, can directly connect to Gnd and Vcc. I also saved the reset lowpass, just connecting pin 6 to Vcc.
- The transmitter can be powered from the 5V rail, helps to reduce regulator load.
- Why the pullups on the I2C pins of the EEPROM? Is that necessary?
- What is the LED good for?
So far I've published boards and schematics of all my creations, but with TinyTOSLINK I was hesitant, since there is Hifiberry Digi. TinyTOSLINK is no
clone, I had it ready before
Hifiberry Digi came out, however I've changed the crystal frequeny and I2C address to match it.
Being compatible in this way benefits a lot from the existing software, support and installation instructions for many distros.
Now that the hardware design is kind of public, I'm reconsidering. Anyway, It's not rocket science, one of the most simple boards I've made. The layout was lots of fiddling, especially the tiny rev. B version.