MT3620 Azure Sphere Based Altair 8800 Hardware

The PCB design is adapted from the open source project Altair 8800 emulator created by Daniel Karling. The original design files were created using KiCad, however to update the design, the PCB design file was imported into Altium, which is the format used in this version of the project. The schematic file was not imported, so please refer to Daniel Karling's original project for details.

The updates that we have made to the PCB include:

• The original project was designed to be interfaced to an Arduino which operates at 5V, however the MT3620 operates at 3.3V. It was therefore necessary to replace some of the TTL logic with parts that are 3.3V compatible. In addition, R33 has been replaced with a wire link.
• All of the discrete resistors have been replaced with resistor arrays to help simplify assembly.
• The micro-SD card holder has been replaced with a part that can more easily be hand soldered.
• The switches have been replaced with parts that can more easily be sourced from DigiKey
• The overlay silkscreen has been updated to include the switch and LED functions.

Contents

Folder	Description
Altium	Altium Designer format project and PCB files
Production	Production files including gerber and NC drill files

Instructions

Please refer to the main project documentation for full setup and usage instructions.

Front panel wiring

Seeed Studio Azure Sphere development Kit

Altair Front Panel Pin No.	Function	MT3620 Pin	MT3620 Pin Function	Description
1	Switches Load	H4/P14	GPIO40	Active low load switch data into shift registers
2	Switches Chip Select	H4/P12	GPIO37	Switch 'chip select' - active low enable for shift registers that read switch states
4	MISO	H4/P5	MISO1	SPI MISO
5	MOSI	H4/P11	MOSI1	SPI MOSI
6	MR	H4/P10	GPIO39	Active low master rest of shift registers that control the LEDs
7	CLK	H4/P7	SCLK1	Clock input
8	LED Store	H4/P8	GPIO36	Clocks data from the shift registers into the storage registers that control the LEDs
9	LED Output Enable	H4/P6	GPIO38	Active low output enable for the shift registers that control the LEDs
10	VCC	H3/P3	3.3 V	+3.3 V
11	GND	H3/P2	GND	Ground

Avnet Azure Sphere Starter Kit Rev 1 & 2

Altair Front Panel Pin No.	Function	Click Pin	MT3620 Pin Function	Description
1	Switches load	CLICK 1: AN	GPIO42	Active low load switch data into shift registers
2	Switches Chip Select	CLICK 1: RST	GPIO16	Switch 'chip select' - active low enable for shift registers that read switch states
4	MISO	CLICK 1: MISO	MISO1	SPI MISO
5	MOSI	CLICK 1: MOSI	MOSI1	SPI MOSI
6	MR	CLICK 1: PWM	GPIO0	Active low master rest of shift registers that control the LEDs
7	CLK	CLICK 1: SCK	SCLK1	Clock input
8	LED Store	CLICK 1: INT	GPIO2	Clocks data from the shift registers into the storage registers that control the LEDs
9	LED Output Enable	CLICK 1: RX	GPIO28	Active low output enable for the shift registers that control the LEDs
10	VCC	CLICK 1: 3.3	3.3 V	+3.3 V
11	GND	CLICK 1: GND	GND	Ground

Raspberry Pi Header

Altair Front Panel Pin No.	Function	Raspberry Pi Pin	Pin Function	Description
1	Switches load	29	GP 05	Active low load switch data into shift registers
2	Switches Chip Select	27	GP 00	Switch 'chip select' - active low enable for shift registers that read switch states
4	MISO	21	MISO	SPI MISO
5	MOSI	19	MOSI	SPI MOSI
6	MR	15	GP 22	Active low master rest of shift registers that control the LEDs
7	CLK	23	CLK	Clock input
8	LED Store	13	GP 27	Clocks data from the shift registers into the storage registers that control the LEDs
9	LED Output Enable	11	GP 17	Active low output enable for the shift registers that control the LEDs
10	VCC	17	3.3 V	+3.3 V
11	GND	9	GND	Ground

Project expectations

The project is a proof of concept. It is not official, maintained, or production-ready.

Expected support for the code

This project is unsupported.

How to report an issue

If you run into an issue with this project, please open a GitHub issue against this repo.

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.microsoft.com.

When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repositories using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact [email protected] with any additional questions or comments.

License

The license for this project is TBD.