I2C as in comm bus or something else?

[Aclassifier]

I see in the ICE40 Data sheet (page 5, acronyms) that I2C means "Inter-Integrated Circuit". Does that mean not Philips I2C communication bus with SDA and SCL, but some other kind of building block? However, here thay mention I2C and "Communicate via slow UART and I2C interfaces while the microprocessor is asleep" and "Integrated hard I2C and SPI cores that enable flexible device configuration through SPI" in the context of a serial bus (SPI). Are we talking about the serial bus I2C or something else? They also talk about "I2C Core" (two of them) and "SPI core" (two of them) in that document. Not needed to say: I am confused.

Assuming it is I2C communication bus, is this reserved for comms with the STM32? Over which pins? If not, will they communicate over SPI? Looking here I2C is mentioned as "RPI header similar to BlackIce II - I2C, Uart, SPI, SWIO debugging connector". I also find CRX/SCL and CTX/SDA in teh BlackEdge Connectors - but they come from the STM32.

Finally, uploading of netlist (or whatever?) is done to first STM32? or only ICE40? and USB. I cannot find the USB connector in the diagram.

If I2C is not an "I2C uart", is I2C comm Verilog code available that could convert two of the IO pins to SDA and SCL (and perhaps a RES)? I would like to do some I2C comm stuff from Verilog.

Sorry for this messy post!

[lawrie]

I see in the ICE40 Data sheet (page 5, acronyms) that I2C means "Inter-Integrated Circuit".

Yes that is what the acronym stands for. But the hx4k device that Blackice Mx uses has no built-in support for I2C unlike other ice40 devices such as the up5k.

Does that mean not Philips I2C communication bus with SDA and SCL, but some other kind of building block?

Yes, they are referring to Philips I2C.

However, here thay mention I2C and "Communicate via slow UART and I2C interfaces while the microprocessor is asleep" and "Integrated hard I2C and SPI cores that enable flexible device configuration through SPI" in the context of a serial bus (SPI). Are we talking about the serial bus I2C or something else? They also talk about "I2C Core" (two of them) and "SPI core" (two of them) in that document. Not needed to say: I am confused.

Those cores do not exist on the hx4k or hx8k. You have to write your own. (Those cores are not that usable on the chips (like up5k) that do support them. You are often better off using an I2C core tailored to your intended use.)

Assuming it is I2C communication bus, is this reserved for comms with the STM32? Over which pins? If not, will they communicate over SPI? Looking here I2C is mentioned as "RPI header similar to BlackIce II - I2C, Uart, SPI, SWIO debugging connector". I also find CRX/SCL and CTX/SDA in teh BlackEdge Connectors - but they come from the STM32.

The STM32 like other microcontrollers supports I2C and the SDA and SCL pins for one such I2C bus are connected to the RPi header. But there is no support in the firmware for that. There are also SPI pins on the Rpi header shared with the ice40.

Finally, uploading of netlist (or whatever?) is done to first STM32? or only ICE40? and USB. I cannot find the USB connector in the diagram.

Uploading bitstreams makes no use of I2C. The bitstream is sent using a serial connection (actually CDC-ACM) via the USB PRG connetcor (the one in the corner of the IceCore board) to the STM32, which then uses SPI to configure the ice40 device.

If I2C is not an "I2C uart", is I2C comm Verilog code available that could convert two of the IO pins to SDA and SCL (and perhaps a RES)? I would like to do some I2C comm stuff from Verilog.

I2C and UART and SPI are all different serial protocols that can be used on FPGAs and microcontrollers such as the STM32.

On the Blackice Mx you can use a core that you write yourself or find from github or elsewhere to do any of these. For SPI and UART there are some shared pins with the STM32 if you want to communicate with that using those protocols.

The latest STM32 fimware supports UART from the ice40 via the STM32 to the PC host using fpga pins 61 and 62.

If you want to use I2C from the ice40 to a external device connected via Mixmod pins, then you can use any two pins that you choose for SCL and SDA. An I2C core that I use is here

I used a version of that to drive Wii Nunchuks (which are I2C devices) in the Pacman game that I recently posted about.

Sorry if my answer was confusing. There was so much confusion in your questions, that answering them was difficult.
.

[lawrie]

This diagram - https://forum.mystorm.uk/t/new-product-blackice-mx/551/19 might be helpful in showing the various connections between pins on the IceCore board, but it is slightly out of date and not fully implemented in the firmware.

For I2C from the ice40 to an external device, all this is irrelevant. You just use any of the digital pins available on the Mixmods for SCL and SDA and implement your own I2C core on the ice40.

[Aclassifier]

Sorry if my answer was confusing. There was so much confusion in your questions, that answering them was difficult.

Thanks a lot! Yes I know I did some rather nasty brainstorming on my own, that you certainly rectified for me! I am so thankful, @lawrie! But soon I'll have Mx boards to play with (and sw..). Stay tuned.

Aside

The only embarassing point is that even if I have worked with I2C in "a hundred" products since 1982 I guess I wasn't aware of its acronym, which Wikipedia is very clear about - and which I even quoted in the intro. Only recently have I worked with SPI (in the RFM69 based radio board)

[lawrie]

Reading the Lattice documentation can be confusing unless you know the context of it. They describe a whole range of devices so large parts of it are not relevant to hx4k/hx8k that IceCore uses. Also they only describe the ice40 chip, not the specific board we are using with all its specific interfaces. And they describe their own software, and not the open source software that we use.

[AndyCap]

This diagram - https://forum.mystorm.uk/t/new-product-blackice-mx/551/19 might be helpful in showing the various connections between pins on the IceCore board, but it is slightly out of date and not fully implemented in the firmware.

This area still confuses me quite a lot (including that diagram), is there a list somewhere of the connections between the STM and ICE40?

[Aclassifier]

I guess this is related? : I would also have liked to know what "BlackEdge" is. In New Product - BlackIce Mx there is a BlackEdge link look-alike in the first line that isn't. This is what I try to find out about in this question as well. Maybe I should just forget about it and stop mentioning it in my own blog note, because it's some history that is not relevant any more?

[Folknology]

I guess this is related? : I would also have liked to know what "BlackEdge" is

It might be worth going through this presentation, rather than discussing it in this thread about I2C

[lawrie]

I have started a new thread where I attempt to describe all these connections.