Emulate an EPROM - How Hard Could it Be? -- Episode 517

Matt — Fri, 24 Sep 2021 07:24:00 GMT

Current Revision posted to Documents by Matt on 9/24/2021 7:24:00 AM

www.youtube.com/watch

The Apple IIe uses a custom microcontroller and ROM chip to put ASCII values into the computer’s memory. How hard could it be to replace that dual-chip setup with a microcontroller to emulate another kind of keyboard? Bald Engineer tries using an Arduino Mega 2560, Teensy 4.0, and a Pi Pico to replace a vintage ROM chip. See what works AND what does not!

In the attached zip file are:

KiCad files for the ROM Interposer Board
Arduino code for ROM test
Teensy code to test interrupt latency
Python code that can respond to an Output Enable signal

A couple of notes that keep coming up:

Q: Why do you need to emulate a ROM chip anyway?

A: Like most 8-bit computers, the keyboard interface eventually talks directly to the memory bus. In an Apple IIe (and IIc), that is done through a ROM chip.

Q: Why not just replace the keyboard matrix?

A: The final design will not use the original keyboard microcontroller or ROM. Ideally, I want to have an interface for a USB keyboard (and possibly Apple Desktop Bus: ADB.)

Q: The Teensy was only 200 nanoseconds, why not just use that?

A: The Mini-Apple IIe is based on the MEGA-II ASIC from an Apple IIgs. Its timing is tighter and slightly different from the Apple IIe’s MMU. The Teensy is slightly too slow.

Q: What is “Golden Delicious”?

A: Originally, I was naming this project “Golden Delicious.” So, let’s call it a code name. Now, I call it “Mini Apple IIe.” But, the final project has a different name.

Supplemental Content:

Workbench Wednesday 18: Digilent Analog Discovery Review
Workbench Wednesday 16: Instrument Basics: Logic Analyzer
Keyboard ROM (26-pin) Interposer Board: https://github.com/baldengineer/Golden-Delicious/tree/master/kicad%20files/ROM%20Interposer%20board

Bill of Material:

Product Name	Manufacturer	Quantity	Buy Kit
Pi Pico (RP2040)	Raspberry Pi Foundation	1	Buy Now
Mega 2560	Arduino	1	Buy Now
Analog Discovery 2	Digilent	1	Buy Now
Digital Discovery	Digilent	1	Buy Now

Additional Parts:

Product Name
Teensy 4.0 from PJRC

Attachments:

community.element14.com/.../emulating_5F00_rom_5F00_with_5F00_mcu_5F00_v2.zip

element14 Presents | About James| Project Videos

Tags: emulating rom, baldengineer, raspberry pi pico, e14p_JBE, apple, apple iie, eprom, e14presents_baldengineer, masked rom, raspberry pi, digilent, element14 presents, how hard can it be, james, teensy, arduino, friday_release, pi pico

Episode 517: Emulate an EPROM - How Hard Could it Be?

saradetwiler — Thu, 07 Jul 2022 20:38:34 GMT

Revision 9 posted to Documents by saradetwiler on 7/7/2022 8:38:34 PM

www.youtube.com/watch

In the attached zip file are:

KiCad files for the ROM Interposer Board
Arduino code for ROM test
Teensy code to test interrupt latency
Python code that can respond to an Output Enable signal

A couple of notes that keep coming up:

Q: Why do you need to emulate a ROM chip anyway?

A: Like most 8-bit computers, the keyboard interface eventually talks directly to the memory bus. In an Apple IIe (and IIc), that is done through a ROM chip.

Q: Why not just replace the keyboard matrix?

A: The final design will not use the original keyboard microcontroller or ROM. Ideally, I want to have an interface for a USB keyboard (and possibly Apple Desktop Bus: ADB.)

Q: The Teensy was only 200 nanoseconds, why not just use that?

A: The Mini-Apple IIe is based on the MEGA-II ASIC from an Apple IIgs. Its timing is tighter and slightly different from the Apple IIe’s MMU. The Teensy is slightly too slow.

Q: What is “Golden Delicious”?

A: Originally, I was naming this project “Golden Delicious.” So, let’s call it a code name. Now, I call it “Mini Apple IIe.” But, the final project has a different name.

Supplemental Content:

Workbench Wednesday 18: Digilent Analog Discovery Review
Workbench Wednesday 16: Instrument Basics: Logic Analyzer
Keyboard ROM (26-pin) Interposer Board: https://github.com/baldengineer/Golden-Delicious/tree/master/kicad%20files/ROM%20Interposer%20board

Bill of Material:

Product Name	Manufacturer	Quantity	Buy Kit
Pi Pico (RP2040)	Raspberry Pi Foundation	1	Buy Now
Mega 2560	Arduino	1	Buy Now
Analog Discovery 2	Digilent	1	Buy Now
Digital Discovery	Digilent	1	Buy Now

Additional Parts:

Product Name
Teensy 4.0 from PJRC

Attachments:

community.element14.com/.../emulating_5F00_rom_5F00_with_5F00_mcu_5F00_v2.zip

element14 Presents | About James| Project Videos

Episode 517: Emulate an EPROM - How Hard Could it Be?

jdumais — Fri, 11 Mar 2022 15:22:38 GMT

Revision 8 posted to Documents by jdumais on 3/11/2022 3:22:38 PM

www.youtube.com/watch

In the attached zip file are:

KiCad files for the ROM Interposer Board
Arduino code for ROM test
Teensy code to test interrupt latency
Python code that can respond to an Output Enable signal

A couple of notes that keep coming up:

Q: Why do you need to emulate a ROM chip anyway?

A: Like most 8-bit computers, the keyboard interface eventually talks directly to the memory bus. In an Apple IIe (and IIc), that is done through a ROM chip.

Q: Why not just replace the keyboard matrix?

A: The final design will not use the original keyboard microcontroller or ROM. Ideally, I want to have an interface for a USB keyboard (and possibly Apple Desktop Bus: ADB.)

Q: The Teensy was only 200 nanoseconds, why not just use that?

A: The Mini-Apple IIe is based on the MEGA-II ASIC from an Apple IIgs. Its timing is tighter and slightly different from the Apple IIe’s MMU. The Teensy is slightly too slow.

Q: What is “Golden Delicious”?

A: Originally, I was naming this project “Golden Delicious.” So, let’s call it a code name. Now, I call it “Mini Apple IIe.” But, the final project has a different name.

Supplemental Content:

Workbench Wednesday 18: Digilent Analog Discovery Review
Workbench Wednesday 16: Instrument Basics: Logic Analyzer
Keyboard ROM (26-pin) Interposer Board: https://github.com/baldengineer/Golden-Delicious/tree/master/kicad%20files/ROM%20Interposer%20board

Bill of Material:

Product Name	Manufacturer	Quantity	Buy Kit
Pi Pico (RP2040)	Raspberry Pi Foundation	1	Buy Now
Mega 2560	Arduino	1	Buy Now
Analog Discovery 2	Digilent	1	Buy Now
Digital Discovery	Digilent	1	Buy Now

Additional Parts:

Product Name
Teensy 4.0 from PJRC

Attachments:

community.element14.com/.../emulating_5F00_rom_5F00_with_5F00_mcu_5F00_v2.zip

element14 Presents | About James| Project Videos

Tags: emulating rom, baldengineer, raspberry pi pico, apple, apple iie, eprom, e14presents_baldengineer, masked rom, raspberry pi, digilent, element14 presents, how hard can it be, james, teensy, arduino, friday_release, pi pico

Episode 517: Emulate an EPROM - How Hard Could it Be?

kellyhensen — Wed, 23 Feb 2022 23:36:33 GMT

Revision 7 posted to Documents by kellyhensen on 2/23/2022 11:36:33 PM

www.youtube.com/watch

In the attached zip file are:

KiCad files for the ROM Interposer Board
Arduino code for ROM test
Teensy code to test interrupt latency
Python code that can respond to an Output Enable signal

A couple of notes that keep coming up:

Q: Why do you need to emulate a ROM chip anyway?

A: Like most 8-bit computers, the keyboard interface eventually talks directly to the memory bus. In an Apple IIe (and IIc), that is done through a ROM chip.

Q: Why not just replace the keyboard matrix?

A: The final design will not use the original keyboard microcontroller or ROM. Ideally, I want to have an interface for a USB keyboard (and possibly Apple Desktop Bus: ADB.)

Q: The Teensy was only 200 nanoseconds, why not just use that?

A: The Mini-Apple IIe is based on the MEGA-II ASIC from an Apple IIgs. Its timing is tighter and slightly different from the Apple IIe’s MMU. The Teensy is slightly too slow.

Q: What is “Golden Delicious”?

A: Originally, I was naming this project “Golden Delicious.” So, let’s call it a code name. Now, I call it “Mini Apple IIe.” But, the final project has a different name.

Supplemental Content:

Workbench Wednesday 18: Digilent Analog Discovery Review
Workbench Wednesday 16: Instrument Basics: Logic Analyzer
Keyboard ROM (26-pin) Interposer Board: https://github.com/baldengineer/Golden-Delicious/tree/master/kicad%20files/ROM%20Interposer%20board

Bill of Material:

Product Name	Manufacturer	Quantity	Buy Kit
Pi Pico (RP2040)	Raspberry Pi Foundation	1	Buy Now
Mega 2560	Arduino	1	Buy Now
Analog Discovery 2	Digilent	1	Buy Now
Digital Discovery	Digilent	1	Buy Now

Additional Parts:

Product Name
Teensy 4.0 from PJRC

Attachments:

community.element14.com/.../emulating_5F00_rom_5F00_with_5F00_mcu_5F00_v2.zip

element14 Presents | About James| Project Videos

Episode 517: Emulate an EPROM - How Hard Could it Be?

kellyhensen — Wed, 23 Feb 2022 22:56:55 GMT

Revision 6 posted to Documents by kellyhensen on 2/23/2022 10:56:55 PM

www.youtube.com/watch

In the attached zip file are:

KiCad files for the ROM Interposer Board
Arduino code for ROM test
Teensy code to test interrupt latency
Python code that can respond to an Output Enable signal

A couple of notes that keep coming up:

Q: Why do you need to emulate a ROM chip anyway?

A: Like most 8-bit computers, the keyboard interface eventually talks directly to the memory bus. In an Apple IIe (and IIc), that is done through a ROM chip.

Q: Why not just replace the keyboard matrix?

A: The final design will not use the original keyboard microcontroller or ROM. Ideally, I want to have an interface for a USB keyboard (and possibly Apple Desktop Bus: ADB.)

Q: The Teensy was only 200 nanoseconds, why not just use that?

A: The Mini-Apple IIe is based on the MEGA-II ASIC from an Apple IIgs. Its timing is tighter and slightly different from the Apple IIe’s MMU. The Teensy is slightly too slow.

Q: What is “Golden Delicious”?

A: Originally, I was naming this project “Golden Delicious.” So, let’s call it a code name. Now, I call it “Mini Apple IIe.” But, the final project has a different name.

Supplemental Content:

Workbench Wednesday 18: Digilent Analog Discovery Review
Workbench Wednesday 16: Instrument Basics: Logic Analyzer
Keyboard ROM (26-pin) Interposer Board: https://github.com/baldengineer/Golden-Delicious/tree/master/kicad%20files/ROM%20Interposer%20board

Bill of Material:

Product Name	Manufacturer	Quantity	Buy Kit
Pi Pico (RP2040)	Raspberry Pi Foundation	1	Buy Now
Mega 2560	Arduino	1	Buy Now
Analog Discovery 2	Digilent	1	Buy Now
Digital Discovery	Digilent	1	Buy Now

Additional Parts:

Product Name
Teensy 4.0 from PJRC

Attachments:

community.element14.com/.../emulating_5F00_rom_5F00_with_5F00_mcu_5F00_v2.zip

element14 Presents | About James| Project Videos

Tags: emulating rom, baldengineer, raspberry pi pico, apple, apple iie, eprom, e14presents_baldengineer, masked rom, raspberry pi, digilent, element14 presents, james, teensy, arduino, friday_release, pi pico

Episode 517: Emulate an EPROM - How Hard Could it Be?

kellyhensen — Thu, 13 Jan 2022 15:46:08 GMT

Revision 5 posted to Documents by kellyhensen on 1/13/2022 3:46:08 PM

www.youtube.com/watch

In the attached zip file are:

KiCad files for the ROM Interposer Board
Arduino code for ROM test
Teensy code to test interrupt latency
Python code that can respond to an Output Enable signal

A couple of notes that keep coming up:

Q: Why do you need to emulate a ROM chip anyway?

A: Like most 8-bit computers, the keyboard interface eventually talks directly to the memory bus. In an Apple IIe (and IIc), that is done through a ROM chip.

Q: Why not just replace the keyboard matrix?

A: The final design will not use the original keyboard microcontroller or ROM. Ideally, I want to have an interface for a USB keyboard (and possibly Apple Desktop Bus: ADB.)

Q: The Teensy was only 200 nanoseconds, why not just use that?

A: The Mini-Apple IIe is based on the MEGA-II ASIC from an Apple IIgs. Its timing is tighter and slightly different from the Apple IIe’s MMU. The Teensy is slightly too slow.

Q: What is “Golden Delicious”?

A: Originally, I was naming this project “Golden Delicious.” So, let’s call it a code name. Now, I call it “Mini Apple IIe.” But, the final project has a different name.

Supplemental Content:

Workbench Wednesday 18: Digilent Analog Discovery Review
Workbench Wednesday 16: Instrument Basics: Logic Analyzer
Keyboard ROM (26-pin) Interposer Board: https://github.com/baldengineer/Golden-Delicious/tree/master/kicad%20files/ROM%20Interposer%20board

Bill of Material:

Product Name	Manufacturer	Quantity	Buy Kit
Pi Pico (RP2040)	Raspberry Pi Foundation	1	Buy Now
Mega 2560	Arduino	1	Buy Now
Analog Discovery 2	Digilent	1	Buy Now
Digital Discovery	Digilent	1	Buy Now

Additional Parts:

Product Name
Teensy 4.0 from PJRC

Attachments:

community.element14.com/.../emulating_5F00_rom_5F00_with_5F00_mcu_5F00_v2.zip

element14 Presents | About James| Project Videos

Tags: emulating rom, raspberry pi pico, apple, apple iie, eprom, e14presents_baldengineer, masked rom, raspberry pi, arduino, friday_release, pi pico

Episode 517: Emulate an EPROM - How Hard Could it Be?

dychen — Mon, 29 Nov 2021 23:09:15 GMT

Revision 4 posted to Documents by dychen on 11/29/2021 11:09:15 PM

Emulate an EPROM - How Hard Could it Be?

element14 Presents | Bald Engineer: James Lewis' VCP Profile | Project Videos

www.youtube.com/watch

In the attached zip file are:

KiCad files for the ROM Interposer Board
Arduino code for ROM test
Teensy code to test interrupt latency
Python code that can respond to an Output Enable signal

A couple of notes that keep coming up:

Q: Why do you need to emulate a ROM chip anyway?

A: Like most 8-bit computers, the keyboard interface eventually talks directly to the memory bus. In an Apple IIe (and IIc), that is done through a ROM chip.

Q: Why not just replace the keyboard matrix?

A: The final design will not use the original keyboard microcontroller or ROM. Ideally, I want to have an interface for a USB keyboard (and possibly Apple Desktop Bus: ADB.)

Q: The Teensy was only 200 nanoseconds, why not just use that?

A: The Mini-Apple IIe is based on the MEGA-II ASIC from an Apple IIgs. Its timing is tighter and slightly different from the Apple IIe’s MMU. The Teensy is slightly too slow.

Q: What is “Golden Delicious”?

A: Originally, I was naming this project “Golden Delicious.” So, let’s call it a code name. Now, I call it “Mini Apple IIe.” But, the final project has a different name.

Supplemental Content:

Workbench Wednesday 18: Digilent Analog Discovery Review
Workbench Wednesday 16: Instrument Basics: Logic Analyzer
Keyboard ROM (26-pin) Interposer Board: https://github.com/baldengineer/Golden-Delicious/tree/master/kicad%20files/ROM%20Interposer%20board

Bill of Material:

Product Name	Manufacturer	Quantity	Buy Kit
Pi Pico (RP2040)	Raspberry Pi Foundation	1	Buy Now
Mega 2560	Arduino	1	Buy Now
Analog Discovery 2	Digilent	1	Buy Now
Digital Discovery	Digilent	1	Buy Now

Additional Parts:

Product Name
Teensy 4.0 from PJRC

Attachments:

community.element14.com/.../emulating_5F00_rom_5F00_with_5F00_mcu_5F00_v2.zip

Tags: emulating rom, raspberry pi pico, apple, apple iie, eprom, e14presents_baldengineer, masked rom, raspberry pi, arduino, friday_release, pi pico

Episode 517: Emulate an EPROM - How Hard Could it Be?

dychen — Mon, 29 Nov 2021 23:06:05 GMT

Revision 3 posted to Documents by dychen on 11/29/2021 11:06:05 PM

Emulate an EPROM - How Hard Could it Be?

element14 Presents | Bald Engineer: James Lewis' VCP Profile | Project Videos

www.youtube.com/watch

In the attached zip file are:

KiCad files for the ROM Interposer Board
Arduino code for ROM test
Teensy code to test interrupt latency
Python code that can respond to an Output Enable signal

A couple of notes that keep coming up:

Q: Why do you need to emulate a ROM chip anyway?

A: Like most 8-bit computers, the keyboard interface eventually talks directly to the memory bus. In an Apple IIe (and IIc), that is done through a ROM chip.

Q: Why not just replace the keyboard matrix?

A: The final design will not use the original keyboard microcontroller or ROM. Ideally, I want to have an interface for a USB keyboard (and possibly Apple Desktop Bus: ADB.)

Q: The Teensy was only 200 nanoseconds, why not just use that?

A: The Mini-Apple IIe is based on the MEGA-II ASIC from an Apple IIgs. Its timing is tighter and slightly different from the Apple IIe’s MMU. The Teensy is slightly too slow.

Q: What is “Golden Delicious”?

A: Originally, I was naming this project “Golden Delicious.” So, let’s call it a code name. Now, I call it “Mini Apple IIe.” But, the final project has a different name.

Supplemental Content:

Workbench Wednesday 18: Digilent Analog Discovery Review
Workbench Wednesday 16: Instrument Basics: Logic Analyzer
Keyboard ROM (26-pin) Interposer Board: https://github.com/baldengineer/Golden-Delicious/tree/master/kicad%20files/ROM%20Interposer%20board

Bill of Material:

Product Name	Manufacturer	Quantity	Buy KitBuy Kit
Pi Pico (RP2040)	Raspberry Pi Foundation	1	Buy Now
Mega 2560	Arduino	1	Buy Now
Analog Discovery 2	Digilent	1	Buy Now
Digital Discovery	Digilent	1	Buy Now

Additional Parts:

Product Name
Teensy 4.0 from PJRC

Attachments:

community.element14.com/.../emulating_5F00_rom_5F00_with_5F00_mcu_5F00_v2.zip

Tags: emulating rom, raspberry pi pico, apple, apple iie, eprom, e14presents_baldengineer, masked rom, raspberry pi, arduino, friday_release, pi pico

Episode 517: Emulate an EPROM - How Hard Could it Be?

kellyhensen — Fri, 15 Oct 2021 14:02:14 GMT

Revision 1 posted to Documents by kellyhensen on 10/15/2021 2:02:14 PM

Emulate an EPROM - How Hard Could it Be?

element14 Presents | Bald Engineer: James Lewis' VCP Profile | Project Videos

www.youtube.com/watch

In the attached zip file are:

KiCad files for the ROM Interposer Board
Arduino code for ROM test
Teensy code to test interrupt latency
Python code that can respond to an Output Enable signal

A couple of notes that keep coming up:

Q: Why do you need to emulate a ROM chip anyway?

A: Like most 8-bit computers, the keyboard interface eventually talks directly to the memory bus. In an Apple IIe (and IIc), that is done through a ROM chip.

Q: Why not just replace the keyboard matrix?

A: The final design will not use the original keyboard microcontroller or ROM. Ideally, I want to have an interface for a USB keyboard (and possibly Apple Desktop Bus: ADB.)

Q: The Teensy was only 200 nanoseconds, why not just use that?

A: The Mini-Apple IIe is based on the MEGA-II ASIC from an Apple IIgs. Its timing is tighter and slightly different from the Apple IIe’s MMU. The Teensy is slightly too slow.

Q: What is “Golden Delicious”?

A: Originally, I was naming this project “Golden Delicious.” So, let’s call it a code name. Now, I call it “Mini Apple IIe.” But, the final project has a different name.

Supplemental Content:

Workbench Wednesday 18: Digilent Analog Discovery Review
Workbench Wednesday 16: Instrument Basics: Logic Analyzer
Keyboard ROM (26-pin) Interposer Board: https://github.com/baldengineer/Golden-Delicious/tree/master/kicad%20files/ROM%20Interposer%20board

Bill of Material:

Product Name	Manufacturer	Quantity	Buy KitBuy Kit
Pi Pico (RP2040)	Raspberry Pi Foundation	1	Buy NowBuy Now
Mega 2560	Arduino	1	Buy NowBuy Now
Analog Discovery 2	Digilent	1	Buy NowBuy Now
Digital Discovery	Digilent	1	Buy NowBuy Now

Additional Parts:

Product Name
Teensy 4.0 from PJRC

Attachments:

community.element14.com/.../emulating_5F00_rom_5F00_with_5F00_mcu_5F00_v2.zip

Tags: emulating rom, raspberry pi pico, apple, apple iie, eprom, e14presents_baldengineer, masked rom, raspberry pi, arduino, friday_release, pi pico

Episode 517: Emulate an EPROM - How Hard Could it Be?

kellyhensen — Fri, 15 Oct 2021 14:02:14 GMT

Revision 2 posted to Documents by kellyhensen on 10/15/2021 2:02:14 PM

Emulate an EPROM - How Hard Could it Be?

element14 Presents | Bald Engineer: James Lewis' VCP Profile | Project Videos

www.youtube.com/watch

In the attached zip file are:

KiCad files for the ROM Interposer Board
Arduino code for ROM test
Teensy code to test interrupt latency
Python code that can respond to an Output Enable signal

A couple of notes that keep coming up:

Q: Why do you need to emulate a ROM chip anyway?

A: Like most 8-bit computers, the keyboard interface eventually talks directly to the memory bus. In an Apple IIe (and IIc), that is done through a ROM chip.

Q: Why not just replace the keyboard matrix?

A: The final design will not use the original keyboard microcontroller or ROM. Ideally, I want to have an interface for a USB keyboard (and possibly Apple Desktop Bus: ADB.)

Q: The Teensy was only 200 nanoseconds, why not just use that?

A: The Mini-Apple IIe is based on the MEGA-II ASIC from an Apple IIgs. Its timing is tighter and slightly different from the Apple IIe’s MMU. The Teensy is slightly too slow.

Q: What is “Golden Delicious”?

A: Originally, I was naming this project “Golden Delicious.” So, let’s call it a code name. Now, I call it “Mini Apple IIe.” But, the final project has a different name.

Supplemental Content:

Workbench Wednesday 18: Digilent Analog Discovery Review
Workbench Wednesday 16: Instrument Basics: Logic Analyzer
Keyboard ROM (26-pin) Interposer Board: https://github.com/baldengineer/Golden-Delicious/tree/master/kicad%20files/ROM%20Interposer%20board

Bill of Material:

Product Name	Manufacturer	Quantity	Buy KitBuy Kit
Pi Pico (RP2040)	Raspberry Pi Foundation	1	Buy NowBuy Now
Mega 2560	Arduino	1	Buy NowBuy Now
Analog Discovery 2	Digilent	1	Buy NowBuy Now
Digital Discovery	Digilent	1	Buy NowBuy Now

Additional Parts:

Product Name
Teensy 4.0 from PJRC

Attachments:

community.element14.com/.../emulating_5F00_rom_5F00_with_5F00_mcu_5F00_v2.zip

Tags: emulating rom, raspberry pi pico, apple, apple iie, eprom, e14presents_baldengineer, masked rom, raspberry pi, arduino, friday_release, pi pico