Comments on: Raspberry Pi Pico: DS1307 RTC Module – Keep Track of Time (MicroPython)

By: Ron Benson

Ron Benson — Thu, 20 Feb 2025 00:29:56 +0000

Each pre-built module, such as these, will have its own I2C pullup resistors. If there were more than a couple modules on a single bus, hense multiple resistors in parallel, there would eventually be a problem.
However, “In this particular project that is not relevant”

By: Rui Santos

Rui Santos — Fri, 14 Feb 2025 14:05:57 +0000

In reply to PeteF.

Hi.
There isn’t a specific reason.
We used two different buses, but we could have used just one.
In this particular project that is not relevant.
Regards.

By: PeteF

PeteF — Thu, 13 Feb 2025 11:57:46 +0000

In reply to Bryan.

(Taken from https://en.wikipedia.org/wiki/I%C2%B2C)
The number of nodes which can exist on a given I2C bus is limited by the address space and also by the total bus capacitance of 400 pF, which restricts practical communication distances to a few meters. The relatively high impedance and low noise immunity requires a common ground potential, which again restricts practical use to communication within the same PC board or small system of boards.

I didn’t understand the above post either. Ignoring the SPI reference? I think that ABDELKARIM mis understoood what you were asking. You aren’t trying to send the same data to multiple devices at the same time. You are questioning why use to I2C busses when you can address multiple devices (with different addresses) one at a time on one bus. I don’t have a reason why they do that. Other than maybe the need to update a screen more rapidly than you need to read/update the RTC? Like you I don’t see a reason to use 2 busses (Other than because you can)? Be interesting to hear what Rui Santos has to say.

By: Bryan

Bryan — Mon, 27 Jan 2025 20:28:54 +0000

I guess I miss your meaning. I2C (which is the protocol used by both RTC and Display) has addressing to allow the selection of multiple different devices on the same bus. The RTC address is 68H and the display is 3DH. With that said one can see only a single I2C bus is needed. As for not being able to talk to multiple devices simultaneously, that is usually the case as different devices have different internal functions, hence different data needs to be passed. SPI bus has nothing to do with this topic.

By: ABDELKARIM

ABDELKARIM — Sat, 25 Jan 2025 14:36:39 +0000

In reply to Bryan.

Hi Bryan ,
The answer for your question is very simple , i explain to you breifly the differnce between I2C protocol and SPI(Serial Periferal Interface ) in the way they find the destination to send the information ….
SPI has an attribute called master and slaves…. and can distiguish between slaves by their adresses also but it can’t send the same information to 2_slaves at the same time …instead it choose the first slave adress and send information to it …..after that it choose the other adress and send what it need to send …….that’s mean IT CAN’T SEND INFORMATION TO 2_DIFFERENT DESTINATIONS (SLAVES).at the same time…….
But in I2C there is no attribute of adresses (NO MULTI-DESTINATIONS) ……so we have only one bus …..and at the same time we can’t send multible information over the same bus .
Instead to ADRESSES in SPI ,we have multiple BUSES in I2C ……I2C no. 0 I2C0 …… and I2C no. 1….I2C1 , each is separate from other.

By: Bryan

Bryan — Thu, 16 Jan 2025 17:43:02 +0000

If the RTC and the OLED are both I2C driven why use two different I2C ports to drive them?