Building an Extension Card for the TRS Building an Extension Card - PowerPoint PPT Presentation

Tandy Assembly Springfield, OH 11/10/18 Building an Extension Card for the TRS Building an Extension Card for the TRS -80: 80: Lessons Learned from the Lessons Learned from the RetroStoreCard RetroStoreCard Arno Puder & Sascha Häberling Arno Puder & Sascha Häberling Outline: Outline: 1. RetroStore 2. TRS -80 emulator for Android 3. Understanding the I/O Bus 4. Building the RetroStoreCard

TRS -80 Emulator for Android ● Design goals: ○ Well integrated with Android UI. Make use of sdltrs (do not reinvent the wheel!) ○ Features: ● ○ Model I/III text mode with all the features supported by sdltrs. ○ Support for different screen sizes. ○ Retro fonts by Rebecca Bettencourt http://www.kreativekorp.com/software/fonts/trs80.shtml ○ Different soft -keyboard layouts, external keyboard, game controller, tilt interface. ○ Tutorial system. Chromecast support. ○ ○ Sound. Configurations. ○ ● First public release on Google Play Store April 16, 2013. ● Google Play Store listing: https://play.google.com/store/apps/details?id=org.puder.trs80

RetroStore.org Apple and Google made the concept of app stores popular. ● ● Idea: create an app store for vintage platforms. ● Goals: ○ Effortless downloading and installation of retro apps. ○ Support different vintage platforms. ○ Serve as a digital archive preserving retro apps. ● Related approaches: ○ Retrocomputing Archive (http://www.retroarchive.org/) ○ South West Retro Computing Archive (http://www.retro-computing.org/) ○ ClassicCmp (http://www.classiccmp.org/cpmarchives/trs80.php) ○ System 80 Archive ( http://www.classic-computers.org.nz/system-80/software_archive_directory.htm ) ○ Many, many, others... ● Differentiator: we offer open API to access and download retro apps!

RetroStoreCard

RetroStoreCard Overview 1. Push button 2. Multi-color status LED 3. Power indicator 4. Micro-USB connector 5. TRS -80 I/O bus connector

I/O Bus Pins Name Description Pins D[0-7] Data lines 1,3,…,15 A[0-7] Address lines 17,19,…,31 RD * Read in progress 33 WR * Write in progress 35 IORQ * I/O request 49 IOBUS_WAIT * Force wait-states on Z80 41 IOBUS_INT * Signal interrupt to Z80 39

I/O Bus Write Cycle

1 Bit Output D 0 D Q CLK WR * IORQ * A 0 A 1 A 2 A 3 A 4 A 5 A 6 A 7 31 10 = 1F 16 = 00011111 2

Writing to the I/O Bus – First Attempt > OUT31,0 > OUT31,1 > OUT31,0 > OUT31,1

Writing to the I/O Bus – Second Attempt > OUT236,56 > OUT31,0 > OUT31,1 > OUT31,0 > OUT31,1

Writing to the I/O Bus – Third Attempt 10 OUT236,56 20 OUT31,0 30 INPUT X 40 OUT31,1 50 INPUT X 60 GOTO20 RUN

Success!

ESP -W ROOM-32 Low-cost microcontroller including WiFi and Bluetooth. ● Produced by Shanghai-based Chinese manufacturer, Espressif Systems. ● CPU: dual core 32-bit RISC Tensilica Xtensa LX6 @ 240 MHz. ● FreeRTOS ● Flash memory: 4MB ● SRAM : 520 kB ● WiFi: ● IEEE 802.11 b/g/n ○ WEP or WPA/WPA2 authentication, or open ○ networks. Interface: 16 GPIO pins, SPI, I2C, UART, 10 -bit ADC. ● ● Price point: $11

Architecture 1 Native Client (Z80 code) 3 Internet RetroStore Proxy 2 Router RetroStoreCard 1. Type in small BASIC bootstrap application to download Z80 code via the expansion board. 2. Native client uses expansion port to interact with proxy. 3. Proxy uses ESP32's WiFi to connect to the router and communicate with the Retro Store.

RetroStoreCard Protocol Send Receive Description 0x00 101 bytes bootstrap 0x01 <xx xx> CMD Send CMD 0x02 <xx xx> <str> 0x00 Send app title 0x03 <xx xx> <str> 0x00 Send app details 0x04 <xx> Query WiFi status 0x05 <ssid> \t <passwd> Configure WiFi 0x06 <str> Set search parameter 0x07 <b1> <b2> <b3> Send version 0x08 <str> Send WiFi SSID 0x09 <str> Send WiFi IP

Bootstrap 10 OUT236,56 20 OUT31,0 30 FOR X=0TO100:POKE17152+X,IN(31):NEXT RUN SYSTEM *? /17152

Bootstrap 10 OUT236,56 20 OUT31,0 30 FOR X=0TO100:POKE17152+X,INP(31):NEXT RUN SYSTEM *? /17152

All Good Things... ● Summary: ○ RetroStore as a curation and preservation effort for vintage platforms. Building modern extensions is not that complicated! ○ ○ RetroStoreCard allows access for a TRS -80 Model III to the RetroStore. Outlook: ● ○ ROM patch for auto-boot. ○ Expand to other vintage platforms. Reinterpret RetroStoreCard as a general gateway to the Internet. TrsWiki? TrsBox? ○ Complete source and schematics freely available at: ● https:// github.com/apuder/RetroStoreCard Contact: Arno: arno@retrostore.org Sascha: sascha@retrostore.org