lyzby
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Re: Documentation questions I2C and second UART

Mon Feb 06, 2012 11:11 pm

I just scanned the Broadcom Arm documention (thanks very much for that) and a couple of things stood out.

First, which pins are actually brought out to the GPIO interface?

Second, on page 160, it says "I2C slave only operation".  Did I miss something or is this categorical--only I2C slave operation for the r-pi?  I see some indication of 2 I2C interfaces, but couldn't get them clear in my mind.

Third, on page 175, a second UART is mentioned.  Is the one brought out on the GPIO pins the console "mini-UART"?  In the GPIO alternate function table, p.102 and following, it shows that TXD1 and RXD1 (apparently the second UART) are available as the ALT5 function mode for gpio pins 32 and 33.  Are these pins brought out to the exposed GPIO header area?  If they are available, can they be enabled by an ordinary program, or is special magic required?

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johnbeetem
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Re: Documentation questions I2C and second UART

Tue Feb 07, 2012 12:09 am

lyzby said:

Second, on page 160, it says "I2C slave only operation".  Did I miss something or is this categorical--only I2C slave operation for the r-pi?  I see some indication of 2 I2C interfaces, but couldn't get them clear in my mind.
I only just excitedly and very gratefully downloaded the Broadcom ARM doc myself, but I think you want to look at the BSC (Broadcom Serial Controller) on page 28.  It acts as an I2C master.  This is just my guess.

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johnbeetem
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Re: Documentation questions I2C and second UART

Tue Feb 07, 2012 12:38 am

lyzby said:

First, which pins are actually brought out to the GPIO interface?
The RasPi FAQs say that a RasPi board schematic will be released.  Assuming the BCM2835 pin names haven't been redacted then it should be pretty clear which GPIOs are connected up.  Otherwise I hope someone with the information will kindly update the Wiki.

dom
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Re: Documentation questions I2C and second UART

Tue Feb 07, 2012 12:40 am

Looks like general gpio header P1 contains:
0,1,4,
7,8,9,10,11,
14,15,
17,18,21,22,23,24,25,

victhor393
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Re: Documentation questions I2C and second UART

Tue Feb 07, 2012 1:45 am

This is unrelated, but is alternate function "ALT3" for pins GPIO22-25 (SD1_*) assigned to the SD card slot, or is this a second SD interface?

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Gert van Loo
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Re: Documentation questions I2C and second UART

Tue Feb 07, 2012 10:02 am

The SD card on the board is using the top GPIO pins.,

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