WG: Read I2C data with EPICS

["Loeher, Bastian Dr. via Tech-talk" <tech-talk at aps.anl.gov>]

Dear Steve,

[I forgot to add tech-talk in my original reply].


I've been using the excellent drvAsynI2C from Florian Feldbauer with the standard StreamDevice on top to read and write the I2C bus on a Raspberry Pi SBC. This works really well and is easy to set up in EPICS.


Some references:

https://github.com/ffeldbauer/drvAsynI2C
https://github.com/paulscherrerinstitute/StreamDevice


The startup file contains:

## I2C configuration
drvAsynI2CConfigure("$(device)", "/dev/i2c-1", 1)


I2C communication is then described using the StreamDevice protocols such as:

# Board DAC
set_dac {
        out 0x70 0 8;
        out 0x60 "%.2r";
        out 0x70 0 1;
}
get_dac {
        out 0x70 0 8;
        out 0x60 0;
        MaxInput = 3;
        in  0xc0 "%01r" "%*r";
        out 0x70 0 1;
}
get_temperature_card0 {
  # Mux card 0 to 'cpld'
  out 0x71 2;
  # Get data
  # Return 2 bytes
  MaxInput = 2;
  out 0x48 0;
  in "%02r";
}

---

These protocols would then be called from the EPICS database records.

[oops, I see that Florian himself answered just now, so will stop here]

All the best

Dr. Bastian Löher

Data acquisition
Experiment controls
Detector development

R3B - Relativistic reactions with radioactive beams
Gamma spectroscopy


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________________________________________
Von: Tech-talk <tech-talk-bounces at aps.anl.gov> im Auftrag von Mark Rivers via Tech-talk <tech-talk at aps.anl.gov>
Gesendet: Dienstag, 6. Juli 2021 17:48:08
An: Steve Hu
Cc: tech-talk at aps.anl.gov
Betreff: Re: Read I2C data with EPICS

Hi Steve,


This is a fine place to ask that question.


The I2C data could be put into a waveform record and then you can read it with caget.


Can you explain what type of device you are using with I2C and what information do you want to read or write?  Sending binary data to an EPICS client like you describe is not the typical way that EPICS is used.  The EPICS IOC typically converts that binary data from the device into a more human friendly format, like temperature values, etc.

Mark


________________________________
From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Steve Hu via Tech-talk <tech-talk at aps.anl.gov>
Sent: Tuesday, July 6, 2021 3:34 AM
To: tech-talk at aps.anl.gov
Subject: Read I2C data with EPICS

Hello,

I started to use EPICS recently and currently I am learning to use it. I am a french student and I apologize in advance for my bad English.

I just have one question but I don't know if I am in the right place to ask so please tell me if that is the case.
For a project, my internship supervisor want me to use i2c through EPICS and my last problem is to read the data with EPICS IOC like 0x00 0x01 0x02... Is it possible to read these type of data with caget ?

I thank you in advanced for your help.

Sincerely,
Steve Hu.