Single Chip AVR BASIC Computer V0.3

Description

A computer running the TinyBASIC programming language on an ATmega 1284P microcontroller as well as generating composite video signals and reading PS/2 keyboard input. The computer is easy to assemble at home as all components are through-hole. System features include:
- 8bit ATmega microcontroller running at 16MHz (ATmega 1284P).
- Over 7KB of memory available for creating BASIC programs.
- Header for external EEPROM 'cards' which allow full size programs to be saved (using a 25LC640 EEPROM IC); 4KB internal EEPROM available within the microcontroller.
- USBasp programming header allowing easy programming of the computer once assembled.
- Many GPIO pins for connecting to components and other circuits.

Details

This project is a homebrew 8bit computer which runs a BASIC programming language known as TinyBASIC Plus (TBP for short) and can easily be assembled at home. It generates composite video which is supported by many screens (such as TVs) and reads PS/2 keyboard input. Many GPIO pins are available allowing connections to components such as LEDs, potentiometers, sensors and much more. A L7805 regulator is used to make the system more flexible with the power supply which can be used (compared to using no regulator at all) to power the system such as a 9V wall-mounted transformer or a 12V battery. Over 7KB of SRAM is available for writing TBP programs and an 8KB EEPROM card (connected to the storage header) can be used to save full size programs; the ATmega 1284P also has 4KB internal EEPROM available for saving programs to. The system was designed in KiCAD and the following image shows the schematic:

Optionally, a small PCB (EEPROM Card) containing a 25LC640 EEPROM IC can be connected to the system to allow full size programs to be saved. These cards simply connect using a male and female pin header making them easily removable. A header is present on the PCB allowing the user to select which EEPROM to save BASIC programs to (internal or EEPROM card). These cards can be used to transfer BASIC programs between computers, allow other devices (such as an Arduino) to program the cards or to allow full size programs to be saved. The following images show one of the EEPROM cards which was created using the milling process on 0.8mm red PCBs:

The following image shows the schematic diagram for the EEPROM storage cards:

The following image shows the storage header pinout which is used to connect the EEPROM cards to the computer:

PCBs for the single chip computer (V0.3) are available to buy from me through eBay by clicking the "Purchase PCBs" link at the side of this page. The EEPROM card PCBs can be easily made at home using the photo-etching process or if there is enough interest in these EEPROM card PCBs, I will get some manufactured and also put those up on eBay. The "EEPROM Card Files" link goes to a RAR archive which contains the artwork for the EEPROM storage cards (in an .oxps file), the gerber files and the schematic diagram for the storage cards.

The "Firmware" link on this page goes to a RAR archive which contains the TinyBASIC Plus sketch, the TVout library, the PS/2 keyboard library and the SPIEEPROM library (note, the library folders need to be put into the Arduino IDE libraries folder [within documents on windows]).

Once all the components from the component list have been gathered (note, the male pin headers on the component list can be created by cutting down a long male pin header strip), they can all be soldered into place and the system is then ready for use. Simply connect a TV, PS/2 keyboard and power source such as a PP3 battery or wall-mounted PSU. If an EEPROM card is connected, set the jumper to the 'C' position to allow BASIC programs to be saved to the card or if internal EEPROM is going to be used, set the jumper to the 'I' position (note, the jumper is the same as the type used for IDE hard drive pins used to select master or slave mode so they can easily be found within old computers).

Components

1 × ATmega 1284P 8bit Microcontroller

1 × L7805 Power Management ICs / Linear Voltage Regulators and LDOs

1 × 0.33uF Electrolytic Capacitor

1 × 0.1uF Electrolytic Capacitor

2 × 22pF Ceramic Capacitor

Project Logs

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PCBs & Component Kits
Dan • 05/16/2015 at 22:32 • 0 comments

More PCBs and component kits are now available on eBay and to purchase directly through PayPal. Visit my website for the links: http://www.danselectronic.systems/projects/avr-basic-computer-v0-1/
I currently have 10 kits available and 15 PCBs.
New PCBs
Dan • 12/06/2014 at 20:25 • 0 comments

The design of this computer has been updated and I have PCBs available for sale through eBay (using the link on the left - "Purchase PCBs"); the direct link: http://www.ebay.co.uk/itm/121510974344
A new page dedicated to this new computer design has been created: https://hackaday.io/project/3537-avr-basic-computer-v01
This design includes an additional EEPROM IC to allow full size BASIC programs to be saved. The PCBs are white in colour with ENIG finish.
New Boards
Dan • 11/26/2014 at 20:01 • 1 comment

I received the new boards at the end of last week (one of them can be seen in the image - white PCB with ENIG finish and black silkscreen) and will be assembling one of them this weekend (the plan was to do it today but I haven't received all of the components yet). The remaining boards will be put on eBay once I have assembled one.
As mentioned in the previous log post, this board is a new design which adds an additional IC (an EEPROM IC) to the single chip computer which allows full size programs to be saved.
Update (28/11/14): I still haven't yet received the two capacitors for the voltage regulator (C1 and C2 in the picture) but I will be assembling the rest of the board this weekend. Once I receive the capacitors and test the board, the remaining boards will be put up on eBay. Hopefully they will come on Monday so I can have the board completed the same day.
New Design & More PCBs
Dan • 11/10/2014 at 00:09 • 0 comments

I have taken the design of this computer one step further and added an SPI EEPROM IC on-board allowing full size (over 7KB) BASIC programs to be saved. The following image shows the prototype PCB of this new design:
This PCB was created using the PCB Train 1 day turnaround prototype manufacture service to ensure the new design works (not shown on the above PCB is a power LED which was added after this PCB was ordered). As can be seen from the following image, the new design works correctly so I will be ordering a batch of PCBs and will be putting them on eBay.
A BASIC program was actually already stored in the EEPROM IC (as I took the IC from the red EEPROM cards shown in the details section of this page) and was loaded upon booting the computer showing EEPROM access works correctly.
I will be ordering the batch of PCBs now (they will be white in colour with ENIG finish) and will post when they have arrived. Also, the name of the computer has been changed from "Single Chip Computer" to "AVR BASIC Computer V0.1" due to addition of another IC.

View all 4 project logs

Build Instructions

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Step 1

These instructions will explain how to program the AVR bootloader and firmware using the Arduino IDE on a Windows system.

The Bootloader

After downloading the firmware and the bootloader files (bootlader can be downloaded as a ZIP from the github page), the bootloader files need to placed within the Arduino "hardware" folder and the firmware files need to placed within the Arduino "libraries" folder and the Arduino sketches folder. As can be seen from the image below, copy the ATmega 1284P bootloader folder ("mighty-1284p-master") into the hardware folder within the Arduino directory (Documents -> Arduino -> hardware):

Next, open the Arduino IDE and set the board to "Original Mighty 1284p 16MHz" and the programmer to "USBasp; both are done under the tools menu as shown in the below images:

The bootloader which is programmed to the AVR must be "Original Mighty 1284p 16MHz" as glitches with TVout are caused using the optiboot bootloader.

Note, an Arduino acting as an ISP can be used to program the single chip computer if a USBasp programmer is not available. Google "Arduino ISP" for instructions on how to do this (the SPI pins of the ATmega 1284P are mapped to the USBasp header - pinout for this header can be found by googling "USBasp pinout").

Once the board type and the programmer have been selected, the single chip computer can be powered up and the programmer connected. "Burn Bootloader" can then be selected within the tools menu; once this is completed the bootloader has been burnt to the AVR.

Step 2

The Firmware

After extracting the firmware RAR archive, four of the folders have to be moved into the Arduino "libraries" folder (Documents -> Arduino -> libraries) and one of them into the Arduino sketches folder. The following image shows the folders which need to be copied into the Arduino "libraries" folder (highlighted on the left - "ps2uartKeyboard", "SpiEEPROM", "TVout", "TVoutfonts"):

Next, the remaining folder ("Single_Chip_Computer_V0_3_EEPROM_Cards") needs to be copied into the Arduino sketches directory (Documents -> Arduino) as shown in the following image:

If the Arduino IDE is already open, close it, reopen it and load the single chip computer sketch:

To upload the firmware (the sketch), select "Upload Using Programmer" from the file menu:

Once the sketch has been uploaded to the computer, the programmer can be disconnected. The computer is can then be connected to a TV and a keyboard and used to write BASIC programs.

Discussions

freefuel wrote 03/17/2022 at 15:28

Are the board files available, and if so where can they be found?

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marcelo.senio wrote 03/16/2022 at 12:38

I can't get the input command to work. Can someone explain it to me.

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Dusan Petrovic wrote 10/29/2019 at 13:08

Love your project, very cool.

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f4grx wrote 10/25/2019 at 06:08

hello,

beautiful project.

What EEPROM data format did you use to store BASIC files?

Something existing, or did you come up with something custom?

Thanks

Sebastien

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Andrey Skvortsov wrote 08/23/2017 at 09:24

This is my breadboard-soldering variant with Terminal-BASIC https://hackaday.io/project/22036-terminal-basic firmware:

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howardthecow wrote 04/07/2017 at 00:19

Dan,

All,

Having a problem with the vertical hold on the display

the video out is scrolling downward

any ideas for a fix?

also has the lack of back space on the key board been fixed?

JDH

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Andrey Skvortsov wrote 05/04/2017 at 08:24

Have you tried dong the recommendations https://github.com/encukou/arduino-tvout/issues/35

Similar suggestion to experiment with TVout library haedware specefic macros are on the TVout related forums.

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marcelo.senio wrote 03/12/2022 at 20:27

This in PALM change to NTSC

Line 1942 +/- ok

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Andrey Skvortsov wrote 03/09/2017 at 13:15

Great project.

I'm intereseting in porting my Terminal-BASIC https://sourceforge.net/projects/terminal-basic/

to this board.

It's more powerful BASIC interpreter with support of floating point numbers, multidimensional arrays,

SD cards. Currently It can output via Serial, UTFT library or TVout library. Only PS/2 support need to be done.

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SirWolf wrote 12/12/2017 at 13:57

The PS/2 support is crucial IMHO. It would be very nice to have it. Can you do it, please? :)

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Kipper wrote 08/06/2016 at 20:06

Wheres the download to the arduino project file? this is not really possible without it

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freefuel wrote 02/23/2016 at 21:36

What are the correct fuse bit settings for the 1284p chip? what size shouold the boot loader area be set to?

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freefuel wrote 02/23/2016 at 21:34

can we have the SD card connector first, and do the bug fixing later? please

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torrex90 wrote 02/18/2016 at 04:26

HI, i'm trying to upload the firmware but I've lot of errors that i don't know how can I solve....

EXAMPLE:

Single_Chip_Computer_V0_3_EEPROM_Cards:300: error: size of array 'program' is negative
static unsigned char program[kRamSize];

It's a problem of the sketch? I haven't changed the code!

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freefuel wrote 02/23/2016 at 21:36

what version of the Arduino IDE Are you using? have you have issue with the 1284p chip becoming nonresponsive after the first sketch is loaded?

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torrex90 wrote 02/24/2016 at 01:00

Hi freefuel, I've downloaded an old version of the IDE and I think that it works, but I can't test yet because I haven't the RCA and PS2 connectors, when I test it with the completed circuit I send some info if you want!

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freefuel wrote 02/24/2016 at 01:24

I should try mine again as I have the PS/2 and RCA connectors, but the video capture dongle I ordered is still on the boat.

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torrex90 wrote 03/11/2016 at 18:52

Im trying now to connect it to the TV but it doesn't works.... Have you Telgram account or any similar. I think that maybe it's interesting to stay online bro. ;)

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[deleted]

[this comment has been deleted]

torrex90 wrote 03/11/2016 at 18:55

Hi pablo, as you go with the project?

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Radu Motisan wrote 02/15/2015 at 19:24

Any news on this? Hope you will continue developing it!

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howardthecow wrote 12/04/2014 at 05:10

please keep us posted - JDH
all the best!

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Dan wrote 12/06/2014 at 20:20

Hi JDH,

I have assembled one of the new PCBs and they work fine so will be putting them on eBay within the next couple of days. I will email you when I have done it.

Dan

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howardthecow wrote 12/07/2014 at 00:50

Thanks
That would mean a lot to me
All the best
Jdh

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howardthecow wrote 11/24/2014 at 00:35

Looking forward to it
All the best
JDH

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howardthecow wrote 11/23/2014 at 03:21

Dan,
Any up dates on the new PCB?
All the best
Jdh

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Dan wrote 11/23/2014 at 14:43

Hi JDH,

I have received the new boards and will be assembling one of them on Wednesday to ensure everything works correctly (I will then put them on eBay).

Regards,
Dan

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howardthecow wrote 11/01/2014 at 17:18

Dan,
will you be offering more boards? please let us know, thnaks JDH

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Dan wrote 11/01/2014 at 19:29

Hi JDH,

I will be ordering more boards within the next week or two but they will have a slightly adapted (improved) design to the current one. The following has been changed:
- Removal of the power LED
- Laying down of the L7805 regulator
- Addition of a 25LC640 64K SPI IC to the board (allowing full size programs to be saved)
- Name changed as the current name can no longer be applied (due to the additional IC)

Before I order a large batch of PCBs I will order a single PCB from a manufacturer here in the UK to ensure the new design works correctly (this PCB will be ordered on Monday so I should have it assembled by the end of the week). The batch of PCBs will most likely be white in colour with ENIG finish.

If anyone has any naming suggestions as to what to call the computer, I would like to here them.

Regards,
Dan

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howardthecow wrote 11/02/2014 at 11:19

To bad the power led had to go
Thanks for the heads up

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Dan wrote 11/02/2014 at 11:29

I will add the LED again :) there should be enough space.
Dan

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howardthecow wrote 11/03/2014 at 00:54

Sweet!

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howardthecow wrote 11/03/2014 at 00:54

Really nice work by the way!!!!!

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ArsenioDev wrote 10/25/2014 at 01:23

Hello, I would like to purchase one of these PCBs or the completed computer as a christmas gift for my sister.

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ArsenioDev wrote 10/25/2014 at 01:23

Hello, I would like to purchase one of these PCBs or the completed computer as a christmas gift for my sister.

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howardthecow wrote 09/06/2014 at 21:27

This is so intriguing, back in the day I had an old Atari 400 that used plug in modules for games etc, one of these was Basic - plugged into a tv and even had a manual for " basic" programming lingo , how cool is this!
Semper fi
All the best
JDH

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Single Chip AVR BASIC Computer V0.3

Description

Details

Components

Project Logs

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PCBs & Component Kits

New PCBs

New Boards

New Design & More PCBs

Build Instructions

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Discussions

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