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Re: [Discuss-gnuradio] FrontEnd4702 take 29
From: |
Matt Ettus |
Subject: |
Re: [Discuss-gnuradio] FrontEnd4702 take 29 |
Date: |
Wed, 25 Feb 2004 15:29:46 -0800 |
User-agent: |
Internet Messaging Program (IMP) 4.0-cvs |
Quoting Eric Blossom <address@hidden>:
> 4702 I2C Whackiness
> -------------------
>
> The 4702 can decode at 4 different addresses, but does it though one
> pin. Matt will work up a simple circuit that uses the I2C_A0 and A1
> bits as input and drives the magic pin correctly. This will ensure
> that the 4702 board needs no jumpers and will perform properly in any
> RX slot.
Here goes:
A0 Tells you whether this is a TX or an RX board. 0 = TX, 1 = RX. Since we are
only talking about RX boards for the 4702, this won't matter.
A1 Tells you whether you are in the first or second TX/RX pair. A1=0 means you
are on side A, A1=1 means side B. This is the one we are interested in.
The simplest way to control the addresses on the 2 4702s on each board is this:
On one of the 4702s, the Address select line should be tied to the drain of an
N-MOS transistor. The source of the transistor should go to ground. The gate
goes to A1. Thus, when A1 = 0 (i.e. Unit A), the AS line will be OPEN. When
A1 = 1 (i.e. Unit B), the AS line will be Grounded.
On the other 4702, the AS line should go to a 15 K resistor to +5V. There
should be the source and drain of a P-MOS transistor in parallel with it. When
the P-MOS is off, AS is in the "15K" configuration. When the P-MOS is on, AS
is at +5V. The gate of the P-MOS is connected to both a 10K resistor to +5V
and to the drain of an N-MOS. The P-MOS is controlled by the drain of an
N-MOS. This second N-MOS should have its source at ground, and its gate should
connect to A1.
This covers all 4 addresses for the 4702, there are no jumpers, everything is
automatic when you plug it in, it only takes 2 resistors, 2 N-MOS transistors,
and one P-MOS. You can use the cheapest, lowest current, slowest transistors
you can find, as long as they have a Vds higher than 5V. I hope everyone can
be happy now.
Matt
- Re: [Discuss-gnuradio] frontend4702 schematic and layout, (continued)
- Re: [Discuss-gnuradio] frontend4702 schematic and layout, Matt Ettus, 2004/02/23
- Re: [Discuss-gnuradio] frontend4702 schematic and layout, cfk, 2004/02/23
- Re: [Discuss-gnuradio] frontend4702 schematic and layout, Eric Blossom, 2004/02/24
- Re: [Discuss-gnuradio] frontend4702 schematic and layout, Matt Ettus, 2004/02/24
- [Discuss-gnuradio] FrontEnd4702 take 2, cfk, 2004/02/24
- Re: [Discuss-gnuradio] FrontEnd4702 take 2, Matt Ettus, 2004/02/25
- Re: [Discuss-gnuradio] FrontEnd4702 take 2, John Gilmore, 2004/02/25
- Re: [Discuss-gnuradio] FrontEnd4702 take 2, Eric Blossom, 2004/02/25
- Re: [Discuss-gnuradio] FrontEnd4702 take 2, Matt Ettus, 2004/02/25
- Re: [Discuss-gnuradio] FrontEnd4702 take 29, Eric Blossom, 2004/02/25
- Re: [Discuss-gnuradio] FrontEnd4702 take 29,
Matt Ettus <=
- Re: [Discuss-gnuradio] FrontEnd4702 take 2, Matt Ettus, 2004/02/25
- [Discuss-gnuradio] Better link to front end layout, cfk, 2004/02/25
- Re: [Discuss-gnuradio] Better link to front end layout, Matt Ettus, 2004/02/26
- [Discuss-gnuradio] New FrontEnd Schematic & Layout, cfk, 2004/02/26
- Re: [Discuss-gnuradio] New FrontEnd Schematic & Layout, Eric Blossom, 2004/02/27
- Re: [Discuss-gnuradio] FrontEnd4702 take 2, John Gilmore, 2004/02/25
- Re: [Discuss-gnuradio] frontend4702 schematic and layout, Eric Blossom, 2004/02/24
- Re: [Discuss-gnuradio] frontend4702 schematic and layout, Matt Ettus, 2004/02/24