No there are not. That is why I am saying you need them on the expansion
board. The reason there is no buffer on the board is because it had to be
cheap and fit in an Altoids box. I could not do that and add the buffer,
By buffers I mean like the one used on the LCD board.
https://github.com/CircuitCo/BeagleBone-LCD7-RevA3/blob/master/BeagleBone-LCD7-RevA3-schematic.pdf?raw=true
Look at U1. Replace the VDD_LCD with 1.8V.
Gerald
On Wed, Oct 8, 2014 at 1:48 PM, Bremenpl <[email protected]> wrote:
> I am only asking, no hard feelings :p. Ive just noticed that there were
> no buffers on the lcd lines between nxp and mcu on the bbb. Thats why I
> asked. Why are there no buffers on the bbb? By buffers do you mean that a
> voltage follower would do if the inputs are 3.3V tollerant?
>
> Dnia 8 października 2014 20:44:37 Gerald Coley <[email protected]>
> napisał(a):
>
>> It already is powered from 1.8V. The processor however, is powered from
>> 3.3V. The NXP part is 3.3V tolerant.
>>
>> You need the buffer to clean up the signals and provide better drive as
>> is being done on the LCD boards..
>>
>> I just designed the BeagleBone Black. You are designing your mother board
>> so do as you see fit.
>>
>> Gerald
>>
>>
>> On Wed, Oct 8, 2014 at 1:37 PM, Bremenpl <[email protected]> wrote:
>>
>>> Cant I just power the NXP from 1.8V? If the lines are 1.8V I would
>>> need no translation then. Also there are no buffer on the bbb itself so why
>>> would I need such?
>>>
>>> Dnia 8 października 2014 20:12:06 Gerald Coley <[email protected]>
>>> napisał(a):
>>>
>>>> It is the low voltage level as these are 1.8V inputs. The issue is
>>>> making sure you get low enough, fast enough due to capacitance and at the
>>>> correct frequency to yield a good data integrity. You can try using a
>>>> translator buffer from 3.3V to 1.8V. That should help.
>>>>
>>>>
>>>> Gerald
>>>>
>>>>
>>>> On Wed, Oct 8, 2014 at 12:55 PM, Bremenpl <[email protected]> wrote:
>>>>
>>>>> I could do buffers as well, thats not a problem. I am building the
>>>>> board from scratch. Besides, arent the nxp input very high impedance?
>>>>>
>>>>> Dnia 8 października 2014 19:52:48 Gerald Coley <[email protected]>
>>>>> napisał(a):
>>>>>
>>>>>> I am talking about you adding two NXP parts on those lines as you
>>>>>> indicated that you were doing. LCD cape uses buffers do boost the
signal.
>>>>>> The NXP pins are 1.8V inputs.
>>>>>>
>>>>>> Gerald
>>>>>>
>>>>>> On Wed, Oct 8, 2014 at 12:38 PM, Bremenpl <[email protected]> wrote:
>>>>>>
>>>>>>> There are resistors on the lines, worse case scenarion I can take
>>>>>>> them off. But tgose lines are used for lcd cape already so it does
work,
>>>>>>> whats the problem?
>>>>>>>
>>>>>>> Dnia 8 października 2014 19:06:54 Gerald Coley <
>>>>>>> [email protected]> napisał(a):
>>>>>>>
>>>>>>>> I doubt it will work but you are free to try. Adding two loads such
>>>>>>>> as that on those pins is asking for trouble.
>>>>>>>>
>>>>>>>> Gerald
>>>>>>>>
>>>>>>>>
>>>>>>>> On Wed, Oct 8, 2014 at 1:50 AM, bremenpl <[email protected]>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Hello there,
>>>>>>>>> I am currently working on a motherboard for the BeagleBone Black.
>>>>>>>>> One of the requiments is to have a HDMI output on the side of the
>>>>>>>>> motherboard. I Know that there are LCD pins on the BeagleBone
Black header
>>>>>>>>> and there is a possibility to connect a LCD cape. I was wondering
either it
>>>>>>>>> would work to duplicate the NXP HDMI framer circuit that is on
the board to
>>>>>>>>> the motherboard and use it for hdmi output? If I am correct the only
>>>>>>>>> difference would be that there is no acces to I2C0 from headers
so I would
>>>>>>>>> have to use I2C1/2 for the NXP chip. That way at least I wont
chave to
>>>>>>>>> worry about addressing 2 chips at once (not sure If you can
change address
>>>>>>>>> of the hdmi framer yet).
>>>>>>>>>
>>>>>>>>> My question is, would this solution be bard to implement in
>>>>>>>>> software, or is it easy to change the I2C bus config for hdmi?
Are there
>>>>>>>>> any obstacles that I am not aware of? I would really aprichiate
any help in
>>>>>>>>> here.
>>>>>>>>>
>>>>>>>>> --
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