Re: [Gumstix-users] GPIO source/sink current limits?

[Marc H. <mhu...@lo...>]

Scott,

Start with this.

I'll see what I can review for actual I/O current ratings.

This is from the readme that accompanies the IBIS i/o models.

Marc


------------------------------------------------------------

2.5 volt memory-->PXA2x025.ibs 

3.3 volt memory-->PXA2xO33x1.ibs and PXA2x033x2.ibs

PXA2x033 uses both single and double strength buffers. 
PXA2x033x1 for single strength
PXA2x033x2 for double strength

The split is as follows:

Double strength:

   Memory Bus pads -
MD[*]
MA[*]
NCS[*]
NSDCS[*]
SDCKE[*]
SDCLK[*]
NOE
NWE
NSDCAS
NSDRAS
RDNWR
RDY (GPIO[18])
DQM[*]

  Some PCMCIA pads:
NPOE (GPIO[48])
NPWE (GPIO[49])

  Some peripheral pads:
NACRESET
SYSCLK (GPIO[32])
MMCMD
MMDAT

  JTAG output:
TDO

Single Strength Pads:
All other output and I/O pads except UDC_P and UDC_N, including the LCD
outputs,
MMCLK, and the remaining PCMCIA pads.

Note: The UDC pads use specially modified pads which conform to the USB
spec.


> -----Original Message-----
> From: gum...@li... [mailto:gumstix-users-
> bo...@li...] On Behalf Of Scott Harris
> Sent: Friday, April 04, 2008 8:16 PM
> To: gum...@li...
> Subject: [Gumstix-users] GPIO source/sink current limits?
> 
> After some searching, I'm confused regarding the current limits of the
> GPIO pins.
> 
> Looking at table 10 in the PXA255 electrical specs I'm confused about
> the difference between a high-strength and a low-strength IO pin. I
> searched the other PXA255 docs and couldn't find the high-strength
> term defined anywhere.
> 
> How much current can the GPIO pins sink/source? 3/10 mA? Why is an
> output high current listed as -10 mA? That seems like a sink current.
> Are there two different classes of current capability among the GPIO
> pins?
> 
> Thanks,
> -Scott
> 
> Excerpt from the PXA255 electrical specs:
> 
> Targeted DC Specifications
> The DC characteristics for each pin include input-sense levels and
> output-drive levels and currents.
> These parameters can be used to determine maximum DC loading, and also
> to determine maximum
> transition times for a given load. Table 10, "Standard Input, Output,
> and I/O Pin DC Operating
> Conditions" shows the DC operating conditions for the high- and
> low-strength input, output, and
> I/O pins. All DC specification values are valid for the entire
> temperature range of the device.
> 
> 
> IOH_H Output High Current, all standard, highstrength
> output and I/O pins (VO=VOH) -10 mA
> 
> IOH_L Output High Current, all standard, lowstrength
> output and I/O pins (VO=VOH) -3 mA
> 
> IOL_H Output Low Current, all standard, highstrength
> output and I/O pins (VO=VOH) 10 mA
> 
> IOL_L Output Low Current, all standard, lowstrength
> output and I/O pins (VO=VOH) 3 mA
> 
> 
> On Fri, Apr 4, 2008 at 3:30 PM, Scott Harris <sco...@gm...>
> wrote:
> > I need a few bits of I/O. Is there way to achieve this with the 20
> >  pins on the console-st? I'd like to run a few LEDs and check the
> >  status of a few switches. Ideally, I'd like to do this via Python. My
> >  data rate required is very low.
> >
> >
> >  If this isn't possible, what's my minimum energy path? I need CF (or
> >  MMC for storing data and moving it to a PC), two serial ports, and a
> >  few bits of I/O.
> >
> >  Thanks,
> >  -Scott
> >
> 
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