Control PCA9635 via I2C from MBHP

Design Concepts
1

Hello,

I would like to control something like 40 PCA9635 (16 Channel LED PWM drivers with I2C interface) from MBHP. I know there is the IIC module, but that one allows only four slaves. My data rate on the I2C bus would be rather low, only a couple of LEDs to change from time to time, so overload should be no issue, I think.

Still, I do not know how to connect the I2C bus to a MBHP core, who will act as the I2C master. I could either use a MBHP core that is already being used for a MIDIBox128, or use a dedicated MBHP core. The adressing needs seven bits, and I do not know how to handle that from MBHP.

What do you think?

2

I think you should google for the datasheet so I don’t have to :wink:

3

Well, I did look for the datasheets for the PICs and the PCA6935. I know that this is possible, but I wanted to know how easy it would be to adapt MIOS to do that. Sorry if I did not formulate my question very clearly…

Best, ALEXander.

4

I wanted to know how easy it would be to adapt MIOS to do that.

You dont have to, MIOS is adapted to that.

Use C.

I know there is the IIC module, but that one allows only four slaves.

There is no “IIC module”, i guess you’re talking about “IIC MIDI module” ?

The theorical IIC slaves number is 128 (or maybe 126).

I guess it’s possible to drive 40 of your chips, if the data rate is not too high.

I would like to try and help you, but i dont have such chips.

http://www.nxp.com/acrobat_download/datasheets/PCA9635_5.pdf

Have a look at page 21-22

I did some IIC experiments, look at the user projects for code samples.

I strongly suggest that you use a dedicated core to do it.

Good luck !

5

Well, I did look for the datasheets for the PICs and the PCA6935. I know that this is possible, but I wanted to know how easy it would be to adapt MIOS to do that. Sorry if I did not formulate my question very clearly…

No, your question was formed well :slight_smile: But, I don’t know the datasheet for the PCA chip from memory… So I’d need to read it, to know how it works, to give you advice on how to use it with MIOS/MBHP. Think about it :wink: Bill has covered it now, anyway :slight_smile:

6

Well, ok, there you have it. I think I will manage, I just hope the I2C Bus really supports that many devices, and that it is not too sensitive to the pwm going on all around it.

7

OK obviously I thought that was funnier than you did ;D

It really does :slight_smile: Interference should not be a problem, but I’d probably put it on a PCB to be sure… There’ve been threads about termination lately too, that could be of interest.

8

Well, I was slightly amused  :wink:

But thanks, I am now really at the point of making the PCB with everything on it.

Has anybody ever made an SMD PCB for the core module?

Cheers, ALEXander.

9

This is a programming example for sending data over IIC:

http://www.ucapps.de/cmios_fun.html#MIOS_IIC_ByteSend

The IIC slaves have to be connected to J4 of the core module

Best Regards, Thorsten.

10

Perfect, thanks! I will keep you posted about progress, but at the moment there is not much to show.

Best, ALEXander.