Internal sdcard interface

P2000T SD-CARD cartridge

Table of contents

• Purpose
• Downloads
• How it functions
• Images
• Commands
• Compilation instructions
• Repository contents
• Building the hardware
• Ordering a cartridge
• Internal SD-card board
• Formatting SD-card
• License

[!TIP] Have questions or comments about the P2000T SD-card cartridge? Join the conversation and chat with the developers on our Discord server.

YouTube

Check out the YouTube video below for a detailed review of the SD-card cartridge.

Purpose

Perhaps the most elegant solution for loading CAS files into your P2000T or making backups of your tapes is via a cartridge that hosts an SD-card slot. Even the smallest SD-cards have enough capacity to store the complete P2000T tape archive. Reading from such an SD-card is non-trivial and requires both a hardware solution to interface with the I/O port of the P2000T as well as a software solution to navigate through the files hosted on a FAT32 partition. This repository contains the PCB for interfacing a P2000T with an SD-card and the necessary software routines to grab .CAS files from said SD card and load them into memory.

[!TIP] Documentation

• Detailed documentation included how-to procedures can be found here
• There is also a manual in Dutch available.

Downloads

Read the section "How it functions" to understand what each download file does.

[!WARNING] The files shown here cater specifically to PCB version 6 or later where the SD-card listens to I/O port 0x4X. Earlier version of the PCB are no longer actively maintained.

• BASICBOOTSTRAP.BIN
• FLASHER.BIN
• LAUNCHER.BIN

[!TIP]

• Precompiled SD-card images, including flashing instructions, can be found here
• A list of PRG programs, specifically designed to operate with the SD-card cartridge, can be found here

How it functions

To interface with the SD-card, an SD-card slot is connected to the I/O port of the P2000T. Interfacing with the SD-card proceeds via the SPI protocol which is encoded in hardware (in contrast to bit-banging the protocol in software). From the perspective of the P2000T, simple 1-byte instructions can be sent and retrieved from the SD-card. By sending specific commands, data is sent or retrieved from the SD-card.

While the SLOT2 cartridge (which hooks up to the I/O port of the P2000T) hosts the circuitry to interface with the SD-card, a SLOT1 cartridge is required that hosts the software. In order to run BASIC programs that are stored on the SD-card as .CAS files, the regular BASIC environment and the required routines to interface with the SD-card need to be present in memory. For this reason, a modified version of the BASIC environment is used which upon boot will load a launcher application from the ROM chip on the SLOT2 cartridge into main memory. This launcher application allows the user to navigate the SD-card and load BASIC programs into memory and run these. Detailed instructions on this process are found here.

The launcher application needs to be placed on the ROM chip by means of a flasher program. The flasher program is a different SLOT1 cartridge which can be downloaded from the download section. The flasher program will copy a LAUNCHER.BIN file from the root folder of the SD-card to the ROM chip on the SLOT2 cartridge. This procedure is also used to update the launcher application. Details on this process can be found here.

It is also possible to make copies of existing tapes to the SD-card. For this purpose, a CASDUMP.PRG program is written. These special types of programs can be loaded from the SD-card and executes via the launcher application. After completion, one automatically returns to the launcher, allowing one to load one of the freshly copied programs.

Images

SLOT2 cartridge enclosure and populated PCB.

Screenshots of navigation and execution of .CAS files.

Commands

Upon booting into the LAUNCHER application, the user interfaces with the SD-card using a set of short commands. Below, the list of commands is provided

Note that <number> needs to replaced with the specific number of a file. Users who are familiar with command line interfaces are probably used to specifying filenames rather than numbers. This reason this approach was chosen is mainly because it is simpler to program and furthermore a bit quicker to type.

Compilation instructions

Compilation is done using the z88dk Docker by means of compile.sh. To compile the launcher, run

cd src
./compile launcher

and for the flasher utility

cd src
./compile flasher

Repository contents

• Cartridge cases
• PCB layout files (KiCAD)
• Modified BASIC ROM source files
• Launcher and Flasher programs
• Custom programs

Building the hardware

Gerber files

To create your own SLOT2 cartridge, download the GERBER files from here, put them in a .ZIP file and send them to your favorite PCB print farm. The author of this repository mainly uses JLCPCB, but plenty of alternatives are available. The SLOT2 PCB has four layers. It is recommended to apply an ENIG (gold) coating and chamfer the edge connector for facile insertion into the P2000T. After ordering, one needs to either hand-solder the components (which can be tricky for the SMD chips) or alternatively make use of an assembly service by which the PCB print farm will solder these components for you.

PCB assembly service

The folder pcb/port2-sdcard-interface contains port2-sdcard-interface_bom_bot.csv and port2-sdcard-interface-bottom-pos.csv which can be used for the JLCPCB assembly service. An example of the part placement can be found in the image below. At the time of writing, two components were unavailable, being the memory chip 62128 and a 0 ohm resistor, which is the reason that these two parts are missing. Note that all through-hole parts, e.g. LEDs, oscillator and PLCC32 socket, have to be hand-soldered in.

Ordering a cartridge

It is also possible to order a cartridge (typically there are always a few of them in stock). If you are interested, feel free to contact the author of this repository at ivo at ivofilot dot nl to discuss pricing and shipping.

Internal SD-card board

This project also includes an internal SD-card board designed to mount on top of the main baseboard inside the P2000T. In addition to the SD-card reader functionality, the board also provides 64 KiB of additional memory, making it an all-in-one solution.

To install this board, you will need two custom brackets. You can find the necessary bracket files here.

Formatting SD-card

The way that the SD-card is formatted is critical. The SD-card needs be formatted using a MBR/FAT32 partition. Often, directly formatting the SD-card via Windows Explorer or similar works well, but sometimes a more rigorous procedure is needed, which is explained below.

1. Type WINDOWS + R and run CMD.
2. Run diskpart.
3. Type list disk followed by select disk <NR> where <NR> corresponds to your SD-card.
4. Type clean. You get a response with DiskPart succeeded in cleaning the disk..
5. Type list volume, followed by select volume <ID> where <ID> corresponds to your SD-card drive.
6. Type convert mbr. You should get the response DiskPart successfully converted the selected disk to MBR format..
7. Type create partition primary. The response should be DiskPart succeeded in creating the specified partition..
8. Finally, type format fs=fat32 quick label="P2000T", after which the response is DiskPart successfully formatted the volume..

Your SD-card should now be ready to work in the SD-cartridge. Of course, you still need to copy files to it in order to load something of it.

License

• All software is shared under the GPL v3 license.
• All hardware (e.g. KiCAD files and .stl files) are shared under the CERN-OHL-S license.
• All documentation is shared under the CC-BY-SA 4.0 license.