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Before I start? — Parallax Forums

Before I start?

dmaruskadmaruska Posts: 13
edited 2008-10-31 11:25 in General Discussion
Hi.· I'm new to the SX community, and to MCU's in general.· I'm a designer, but have left the MCU part to others for selection and program.· But I have a project that I think I can use an SX chip to develop with.· I will need to utilize the I2C to control a number of Relays (100) with.· I will also need to interface a I2C keyboard and Display to.· My question is.· Is this a good choice of Chip to handle the I2C, is the Programming software capable of a number of different I2C devices, I will also have USB interface for remote operation.· Are there example code for I2C integration?· If I wanted to add ADC to the design, What is required here?· I would like to use the SX48BD chip interfaced to MAX7300 chips for relay control.· Any help will be greatly appreciated.

Regards,
Dave M.

Comments

  • BeanBean Posts: 8,129
    edited 2008-10-30 13:49
    Dave,
    Welcome.
    Using the SX48 as an I2C master is pretty straight forward. There are I2C commands in SX/B (the SX BASIC compiler) to talk to I2C devices.
    If you need the SX48 to be an I2C slave, then that is alot harder to do.
    From what you are describing it sounds like you want the SX48 to be the master, so you should be okay.

    It looks like the MAX7300 has two addressing pins. So you should be able to connect 4 of them using only 2 pins on the SX48.

    Bean.

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    ·
  • dmaruskadmaruska Posts: 13
    edited 2008-10-30 14:21
    Thanks Bean,· Yes, the SX will be the master.· What are your thoughs on USB interface?· Straight forward here also?

    Regards,

    Dave M.
  • dmaruskadmaruska Posts: 13
    edited 2008-10-30 14:39
    Bean, I was looking at the DS for the MAX7300, The chip has a unique address schema, With two address pins you can have 16 addresses. See Table 3, sheet 12.

    Regards,

    Dave M.
  • VonSzarvasVonSzarvas Posts: 3,526
    edited 2008-10-31 00:30
    Dave,

    On the google/parallax site/etc... travels, I have come across many examples of projects with usb interfaced to the SX, instead/as well as rs232. For example:
    http://www.parallax.com/Portals/0/Downloads/docs/prod/boards/BOE_USB_D_Schematic.pdf

    It would seem no problem.

    The MAX7300 chip you mention looks like it should be useful for something in the future, so I am glad you mentioned it here smile.gif

    Although if I am reading the datasheet correctly, it will only source 4.5ma / sink 10ma per IO. And you may also need to consider the maximum total capabilities, which may be less than the 28 IO's X 10ma; it might be an issue if you need to switch all relays on at once. Anyhow, you might struggle to find a relay (perhaps a reed relay might) that you can directly connect, so you might need an additional bank of uln2803a's or such.

    Goodluck.
  • dmaruskadmaruska Posts: 13
    edited 2008-10-31 11:25
    Maxwin,· You are correct, I have used this in the past and I coupled it with a ULN2003 driver.· Works great.· I also thank you for the information on the USB.· I ordered my "starter" kit yesterday and should have it next week.· I jazzed to get started.· Also, there is a SPI version of the chip also, just FYI...

    Regards,

    Dave M.
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