#diytech

Rooooound display prototype testing 🌀✨

Reimagined GBC logo and VHS cover box art

Testing Dark Castle with audio on the RP2350 Fruit Jam 🕹️🏰

Jepler spent a bunch of time this week working on getting audio working on the pico-umac port https://github.com/jepler/pico-mac/tree/rp2350-fruitjam to Fruit Jam

. Audio on the hardware we're emulating is pretty straightforward: every scanline of the video generator also pops out one byte of PWM data. We have 370 horizontal lines—352 visible and 18 during the vsync—and a 60.15 Hz refresh rate for 22.255 KHz audio approximately. That data is written to $1FD00 http://www.mac.linux-m68k.org/devel/plushw.php . That data is being piped over I2S to the MAX98357

and to a speaker for now.

So, of course, the first thing we have to try out is Dark Castle

Fruit Jam RP2350B credit-card mini computer with all the fixin's 🍓🍇💾

We were catching up on a recent Hackaday hackchat with Eben Upton (https://hackaday.io/event/202122-raspberry-pi-hack-chat-with-eben-upton) and learned some fun facts: such as the DVI hack for the RP2040 was inspired by a device called the IchigoJam (https://www.hackster.io/news/ichigojam-combines-strawberry-and-raspberry-to-deliver-a-raspberry-pi-pico-powered-educational-micro-66aa5d2f6eec). We remember reading about this back when it was an LPC1114, now it uses an RP2040. Well, we're wrapping up the Metro RP2350 (https://www.adafruit.com/product/6003), and lately, we've been joking around that with DVI output and USB Host support via bit-banged PIO, you could sorta build a little stand-alone computer. Well, one pear-green-tea-fueled-afternoon later we tried our hand at designing a 'credit card sized' computer - that's 3.375" x 2.125", about the same size as a business card (https://hackaday.com/2024/05/07/the-2024-business-card-challenge-starts-now/) and turns out there's even a standard named for it: ISO/IEC 7810 ID-1 (https://www.iso.org/standard/70483.html).

Anyhow, with the extra pins of the QFN-80 RP2350B, we're able to jam a ridonkulous amount of hardware into this shape: RP2350B dual 150MHz Cortex M33 w/ PicoProbe debug port, 16 MB Flash + 8 MB PSRAM, USB type C for bootloading/USB client, Micro SD card with SPI or SDIO, DVI output on the HSTX port, I2S stereo headphone + mono speaker via the TLV320DAC3100 (https://www.digikey.com/en/products/detail/texas-instruments/tlv320dac3100irhbt/2353656), 2-port USB type A hub for both keyboard and mouse or game controllers, chunky on-off switch, Stemma QT I2C + Stemma classic JST 3-pin, EYESPI for TFT displays, 5x NeoPixels, 3x tactile switches, and a 16-pin socket header with 10 A/D GPIO + 5V/3V/GND power pins. The PSRAM will help when we want to do things like run emulations that we need to store in fast RAM access, and it will also let us use the main SRAM as the DVI video buffer.

"See" the Sounds of Classic Mac Audio 🔊🍏

We're working on the Pico-Mac port https://github.com/jepler/pico-mac/tree/rp2350-fruitjam to Fruit Jam https://www.adafruit.com/product/6200 and one thing we really want to add is sound support for classic Mac games and HyperCard stacks.

Flap Flap Flying Toasters on Fruit Jam 🕊️🍞💾

We grew up with a Mac Plus/512K, so getting the Pico-Mac 68000 emulator https://github.com/evansm7/pico-mac working on Fruit Jam https://www.adafruit.com/product/6200 with 1MB+ of RAM was a high priority for those nostalgic vibes.

We've got HSTX DVI output plus PSRAM working https://github.com/jepler/pico-mac/tree/rp2350-fruitjam, which means 4MB RAM—that's the most you could get into a Mac Plus and enough to run System 6! https://en.wikipedia.org/wiki/System_6 Please note that System 7.1 was the pinnacle of software design, but System 6 was also pretty good. System 6 had some nifty features, such as the "Extensions" and "Control Panel" system programs, like After Dark with the famous Flying Toasters https://en.wikipedia.org/wiki/After_Dark_(software).

Note that we're still working on audio, so you can see the high byte of the memory space used for audio that we've mapped into the video RAM for visualization. http://www.mac.linux-m68k.org/devel/plushw.php has more details on how that works - its 8-bit PWM audio reads "one byte per scanline." We'll have that output on the I2S DAC for speaker or headphone output.

Leftovers & layout - WLED board revision A completed!

Sunday night, Babyada went to bed early, so we finished the capture and layout of our WLED board. Thanks to all the suggestions, we were able to implement quite a few!

For power, use USB C PD with switch-select or DC up to 24V; they are diode-OR'd together with PMEG3050

https://www.digikey.com/short/zv22b0pq

into a massive 5A 24V fuse

https://www.digikey.com/short/43qwwtwm

For the 5V regulator, we picked NCP718ASN500T1G

https://www.digikey.com/short/bb9ncc0n

- it's linear, but we don't need a lot of current at 5V. For 3.3V, we went with our trusty TPS54202

https://www.digikey.com/short/c1wnnf94

Upon request, we kept the ICS-43434 I2S microphone

https://www.digikey.com/short/28zwrrhz

and added an IR 38KHz receiver. For external connectivity, there's an ADC/DAC/GPIO #27 breakout on a JST SH 3-pin and I2C on a StemmaQT/Qwiic 4-pin.

We also added a 2x3 breakout header with 3V, GND, and 3 more GPIO so you could connect an external microphone, IR receiver, buttons, or rotary encoder. The terminal blocks have three 5V level-shifted outputs with 100 ohm in-line resistors and power/ground pairs for each. If you need just one more LED strand, the fourth 5V signal is on the 2x3 block.

Rounding out the design are four mounting holes, a reset button, GPIO #0 user button, GPIO LED, and an individual NeoPixel, which could be useful for testing. It's still pretty small, 2" x 1.3". With an ESP32-Mini module, we can pick a PCB or wFL antenna port, and it's an easy swap to make it use an ESP32-Pico, which has 2MB PSRAM.