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Communicating with the Linera EPS throug I2C

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Communicating with the Linera EPS throug I2C

Postby Vaisens » Tue Apr 21, 2009 3:49 am

Hello,

I am working with the Pumpkin DevBoard Rev C, the FM430 and the linear EPS. I am trying to get information from the EPS (telemetry) via the I2C protocol.

I know that an isolation circuit must be done in order to separate SPI from I2C bus. I also know that 2 pull-up (2K2) resistor must be put between p3.1 and vcc, and p3.3 and vcc. Please correct me if anything is wrong.

The question is, I would like to know the address of the linear EPS in order communicate with it (You know, [S|Slave Address|R/W|ACK...]).

Another thing I would like to know is how to ask to the EPS the different things like voltages, currents, etc...

Thank you.

[This message has been edited by Vaisens (edited April 21, 2009).]

[This message has been edited by Vaisens (edited April 21, 2009).]

Vaisens
 
Posts: 2
Joined: Mon Apr 20, 2009 11:00 pm

Re: Communicating with the Linera EPS throug I2C

Postby aek » Tue Apr 21, 2009 7:52 am

Hello.

As per the Linear EPS datasheet, I2C comms are a future enhancement (see p. 1) that has not been released.

This means that the Linear EPS does not currently communicate via I2C.

However, it has the capability to do so, and that is something that you could do yourself, as a project, etc. The source code for the Linear EPS is in the Standard CubeSat Kit software distribution (one missing file is also located in the download area). If you look at the ADC code you'll be able to figure out where all the sampled voltages are, etc. I would suggest you try to build the Linear EPS code with the debugging output ON (see main.h), and then you'll get the hang of what it is doing. Remember that if debug_printf() is enabled, the FET must be attached to the board.

In terms of the hardware I2C connection, with a Rev C FM430, then you'll need to ensure that the various resistors of the I2C isolator (including the pullups) are fitted -- see page 4 of the schematics and the I2C memo in the download area.

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aek
aek
 
Posts: 1888
Joined: Sat Aug 26, 2000 11:00 pm

Re: Communicating with the Linera EPS throug I2C

Postby Vaisens » Tue May 05, 2009 3:15 am

Hello again,

I am now trying to send a byte with the I2C protocol, but I think something is wrong with the SCL speed.

I am a bit confused about how I2CPSC, I2CSCLH and I2CSCLL work. I chose de SMCLK as clock source. SMCLK has a frequency of 7.41 MHz approximately. I need a SCL frequency of 100kHz. So, how the previous registers have to be configured?

Thank you in advance.

[This message has been edited by Vaisens (edited May 06, 2009).]

Vaisens
 
Posts: 2
Joined: Mon Apr 20, 2009 11:00 pm


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