franekz
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B+HAT EEPROM

Sun Apr 16, 2017 5:18 pm

Hi. I have a quite simple question. Does the hat have to have EEPROM IC or it is enough to emulate EEPROM by by the HATs uC? It has exactly the same functionality.
Last edited by franekz on Sun Apr 16, 2017 6:57 pm, edited 1 time in total.

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mikronauts
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Re: B+HAT EEPROM

Sun Apr 16, 2017 6:09 pm

Which hat?

Post a link to the hat you are asking about.
franekz wrote:Hi. I have a quite simple question. Does the hat have EEPROM IC or it is enough to emulate EEPROM by by the HATs uC? It has exactly the same functionality.
http://Mikronauts.com - home of EZasPi, RoboPi, Pi Rtc Dio and Pi Jumper @Mikronauts on Twitter
Advanced Robotics, I/O expansion and prototyping boards for the Raspberry Pi

franekz
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Re: B+HAT EEPROM

Sun Apr 16, 2017 6:30 pm

It is a general question. Not about any particular one.

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mikronauts
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Re: B+HAT EEPROM

Sun Apr 16, 2017 6:33 pm

Sorry, I did not catch that you wanted to emulate the eeprom.

In general, as long as you can emulate the i2c 100% it should work.

There is some danger that if the firmware in the Pi changes, the i2c emulation may need to change.
franekz wrote:It is a general question. Not about any particular one.
http://Mikronauts.com - home of EZasPi, RoboPi, Pi Rtc Dio and Pi Jumper @Mikronauts on Twitter
Advanced Robotics, I/O expansion and prototyping boards for the Raspberry Pi

franekz
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Re: B+HAT EEPROM

Sun Apr 16, 2017 6:54 pm

Logically yes but I have just got another answer from RPi staff stating NO EEPROM - NO HAT!

RPi firmware changes do not affect the way EEPROM (or emulated EEPROM) works.

Strontium
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Re: B+HAT EEPROM

Mon Apr 17, 2017 4:01 am

But an "Emulated" EEPROM is still an EEPROM.

I fail to comprehend how they can specify it has to be an actual EEPROM chip. There is no justification to this. What's inside a discrete EEPROM is not known, it could be a 8051 with a block of Flash. Who knows, and who cares. So in that case, is that an "Emulated" EEPROM? Its not specified HOW the EEPROM does what it does, what is only specified is the pinout and the protocol, re-write life, etc. If you have a device that faithfully implements the 24cXX EEPROM protocol, then it is a serial EEPROM as far as the Raspberry PI is concerned and that's as far as it should go.

Its also an unreasonable technical impediment. An Intelligent Hat has no way to re-write an external EEPROM device when its "configuration" changes, but an Emulated EEPROM does not have this limitation and can, in theory, faithfully reflect the hardware configuration of said "Hat". Which better meets the intention of the EEPROM specification than a discrete EEPROM ever can.

hippy
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Re: B+HAT EEPROM

Mon Apr 17, 2017 11:33 am

The HAT specification is here -

https://github.com/raspberrypi/hats/blo ... gnguide.md

"24Cxx type 3.3V I2C EEPROM must be used"

You can however do whatever you want providing you don't claim "HAT compliance".

Unless the foundation say it is compliant and can be called a HAT; you won't get any definitive answers here on whether what you suggest is HAT compliant or not, only opinions. Only a court could definitively decide if the HAT specification has any legal standing and enforceability, and whether an add-on board with emulated EEPROM is "HAT compliant".

gsh
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Re: B+HAT EEPROM

Wed Apr 19, 2017 2:17 pm

There's no reason you cannot emulate the EEPROM. When we say no EEPROM no HAT then we mean that it must respond to the eeprom challenge at boot time. So as long as you can do that then it's fine.

Gordon
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Gordon Hollingworth PhD
Raspberry Pi - Director of Software Engineering

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