Hi!
Sorry if this is a stupid question, but I haven't found any good info
about the UART levels so I better ask!
Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is on 5V.
Can they talk as it is or do I need a 3.3 to 5V buffer between?
Thanks for any help!
Cheers
/Johan
Is LPC2138 UART levels OK for a 5V part?
Started by ●November 10, 2005
Reply by ●November 10, 20052005-11-10
Short answer, NO.
For any electrical part you can look in the schematics, find the "DC
ELECTRICAL CHARACTERISTICS" section, and check the "INPUT HIGH
VOLTAGE". In your case it's minimum 3.4V, so the 3.3V output from the
LPC2138 won't work. Odd, because most 5V parts have an input high
voltage around 2.5V, as it is with most of my parts on my design.
--- In lpc2000@lpc2..., "fredrikssonjohan" <johan@s...> wrote:
>
> Hi!
>
> Sorry if this is a stupid question, but I haven't found any good info
> about the UART levels so I better ask!
>
> Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is on 5V.
> Can they talk as it is or do I need a 3.3 to 5V buffer between?
>
> Thanks for any help!
>
> Cheers
> /Johan
>
For any electrical part you can look in the schematics, find the "DC
ELECTRICAL CHARACTERISTICS" section, and check the "INPUT HIGH
VOLTAGE". In your case it's minimum 3.4V, so the 3.3V output from the
LPC2138 won't work. Odd, because most 5V parts have an input high
voltage around 2.5V, as it is with most of my parts on my design.
--- In lpc2000@lpc2..., "fredrikssonjohan" <johan@s...> wrote:
>
> Hi!
>
> Sorry if this is a stupid question, but I haven't found any good info
> about the UART levels so I better ask!
>
> Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is on 5V.
> Can they talk as it is or do I need a 3.3 to 5V buffer between?
>
> Thanks for any help!
>
> Cheers
> /Johan
>
Reply by ●November 10, 20052005-11-10
---- Original Message ----
From: "seangra" <sgraham@sgra...>
To: <lpc2000@lpc2...>
Sent: Thursday, November 10, 2005 9:11 PM
Subject: [lpc2000] Re: Is LPC2138 UART levels OK for a 5V part?
> Short answer, NO.
>
> For any electrical part you can look in the schematics, find the "DC
> ELECTRICAL CHARACTERISTICS" section, and check the "INPUT HIGH
> VOLTAGE". In your case it's minimum 3.4V, so the 3.3V output from
> the LPC2138 won't work. Odd, because most 5V parts have an input
> high voltage around 2.5V, as it is with most of my parts on my
> design.
That Vih,min of 3.4V is for the 1-wire pin. I guess Johan wants to
connect the LPC2138 to the RXD and TXD pins which have Vih,min=2.7V,
and he should be okay without buffers.
Karl Olsen > --- In lpc2000@lpc2..., "fredrikssonjohan" <johan@s...>
> wrote:
>>
>> Sorry if this is a stupid question, but I haven't found any good
>> info about the UART levels so I better ask!
>>
>> Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is on
>> 5V. Can they talk as it is or do I need a 3.3 to 5V buffer between?
From: "seangra" <sgraham@sgra...>
To: <lpc2000@lpc2...>
Sent: Thursday, November 10, 2005 9:11 PM
Subject: [lpc2000] Re: Is LPC2138 UART levels OK for a 5V part?
> Short answer, NO.
>
> For any electrical part you can look in the schematics, find the "DC
> ELECTRICAL CHARACTERISTICS" section, and check the "INPUT HIGH
> VOLTAGE". In your case it's minimum 3.4V, so the 3.3V output from
> the LPC2138 won't work. Odd, because most 5V parts have an input
> high voltage around 2.5V, as it is with most of my parts on my
> design.
That Vih,min of 3.4V is for the 1-wire pin. I guess Johan wants to
connect the LPC2138 to the RXD and TXD pins which have Vih,min=2.7V,
and he should be okay without buffers.
Karl Olsen > --- In lpc2000@lpc2..., "fredrikssonjohan" <johan@s...>
> wrote:
>>
>> Sorry if this is a stupid question, but I haven't found any good
>> info about the UART levels so I better ask!
>>
>> Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is on
>> 5V. Can they talk as it is or do I need a 3.3 to 5V buffer between?
Reply by ●November 10, 20052005-11-10
The 3.4V logic high minimum seems to be on the 1-wire side of the
interface. The UART side looks like it has the usual 2.7V minimum
logic high. In that case, it should interface with a CMOS 3.3 volt
part with no difficulty.
-- Dave --- In lpc2000@lpc2..., "seangra" <sgraham@o...> wrote:
>
> Short answer, NO.
>
> For any electrical part you can look in the schematics, find the "DC
> ELECTRICAL CHARACTERISTICS" section, and check the "INPUT HIGH
> VOLTAGE". In your case it's minimum 3.4V, so the 3.3V output from the
> LPC2138 won't work. Odd, because most 5V parts have an input high
> voltage around 2.5V, as it is with most of my parts on my design.
>
> --- In lpc2000@lpc2..., "fredrikssonjohan" <johan@s...> wrote:
> >
> > Hi!
> >
> > Sorry if this is a stupid question, but I haven't found any good info
> > about the UART levels so I better ask!
> >
> > Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is on 5V.
> > Can they talk as it is or do I need a 3.3 to 5V buffer between?
> >
> > Thanks for any help!
> >
> > Cheers
> > /Johan
> >
>
Reply by ●November 10, 20052005-11-10
Sorry, my bad!
2.7V seems a lot more reasonable for input level. So yes, it should
work without a buffer!
--- In lpc2000@lpc2..., "derbaier" <dershu@s...> wrote:
>
>
> The 3.4V logic high minimum seems to be on the 1-wire side of the
> interface. The UART side looks like it has the usual 2.7V minimum
> logic high. In that case, it should interface with a CMOS 3.3 volt
> part with no difficulty.
>
> -- Dave > --- In lpc2000@lpc2..., "seangra" <sgraham@o...> wrote:
> >
> > Short answer, NO.
> >
> > For any electrical part you can look in the schematics, find
the "DC
> > ELECTRICAL CHARACTERISTICS" section, and check the "INPUT HIGH
> > VOLTAGE". In your case it's minimum 3.4V, so the 3.3V output
from the
> > LPC2138 won't work. Odd, because most 5V parts have an input
high
> > voltage around 2.5V, as it is with most of my parts on my design.
> >
> > --- In lpc2000@lpc2..., "fredrikssonjohan" <johan@s...>
wrote:
> > >
> > > Hi!
> > >
> > > Sorry if this is a stupid question, but I haven't found any
good info
> > > about the UART levels so I better ask!
> > >
> > > Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is
on 5V.
> > > Can they talk as it is or do I need a 3.3 to 5V buffer between?
> > >
> > > Thanks for any help!
> > >
> > > Cheers
> > > /Johan
> > >
> >
>
2.7V seems a lot more reasonable for input level. So yes, it should
work without a buffer!
--- In lpc2000@lpc2..., "derbaier" <dershu@s...> wrote:
>
>
> The 3.4V logic high minimum seems to be on the 1-wire side of the
> interface. The UART side looks like it has the usual 2.7V minimum
> logic high. In that case, it should interface with a CMOS 3.3 volt
> part with no difficulty.
>
> -- Dave > --- In lpc2000@lpc2..., "seangra" <sgraham@o...> wrote:
> >
> > Short answer, NO.
> >
> > For any electrical part you can look in the schematics, find
the "DC
> > ELECTRICAL CHARACTERISTICS" section, and check the "INPUT HIGH
> > VOLTAGE". In your case it's minimum 3.4V, so the 3.3V output
from the
> > LPC2138 won't work. Odd, because most 5V parts have an input
high
> > voltage around 2.5V, as it is with most of my parts on my design.
> >
> > --- In lpc2000@lpc2..., "fredrikssonjohan" <johan@s...>
wrote:
> > >
> > > Hi!
> > >
> > > Sorry if this is a stupid question, but I haven't found any
good info
> > > about the UART levels so I better ask!
> > >
> > > Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is
on 5V.
> > > Can they talk as it is or do I need a 3.3 to 5V buffer between?
> > >
> > > Thanks for any help!
> > >
> > > Cheers
> > > /Johan
> > >
> >
>
Reply by ●November 10, 20052005-11-10
Not my business but why use the DS-2480? Its code available for
1-Wire/LPC that works perfectly with the use of one pin and a pull up
resistor. Send you a copy if you like.
/Ake fredrikssonjohan wrote:
> Hi!
>
> Sorry if this is a stupid question, but I haven't found any good info
> about the UART levels so I better ask!
>
> Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is on 5V.
> Can they talk as it is or do I need a 3.3 to 5V buffer between?
>
> Thanks for any help!
>
> Cheers
> /Johan > >. >
>
--
---
Ake Hedman (YAP - Yet Another Programmer)
eurosource, Brattbergavägen 17, 820 50 LOS, Sweden
Phone: (46) 657 413430 Cellular: (46) 73 84 84 102
Company home: http://www.eurosource.se
Kryddor/Te/Kaffe: http://www.brattberg.com
Personal homepage: http://www.eurosource.se/akhe
Automated home: http://www.vscp.org
1-Wire/LPC that works perfectly with the use of one pin and a pull up
resistor. Send you a copy if you like.
/Ake fredrikssonjohan wrote:
> Hi!
>
> Sorry if this is a stupid question, but I haven't found any good info
> about the UART levels so I better ask!
>
> Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is on 5V.
> Can they talk as it is or do I need a 3.3 to 5V buffer between?
>
> Thanks for any help!
>
> Cheers
> /Johan > >. >
>
--
---
Ake Hedman (YAP - Yet Another Programmer)
eurosource, Brattbergavägen 17, 820 50 LOS, Sweden
Phone: (46) 657 413430 Cellular: (46) 73 84 84 102
Company home: http://www.eurosource.se
Kryddor/Te/Kaffe: http://www.brattberg.com
Personal homepage: http://www.eurosource.se/akhe
Automated home: http://www.vscp.org
Reply by ●November 11, 20052005-11-11
Can you upload the code ? Thanks !
Regards,
Martin
----- Original Message -----
From: "Ake Hedman, eurosource" <akhe@akhe...>
To: <lpc2000@lpc2...>
Sent: Thursday, November 10, 2005 10:25 PM
Subject: Re: [lpc2000] Is LPC2138 UART levels OK for a 5V part? Not my business but why use the DS-2480? Its code available for
1-Wire/LPC that works perfectly with the use of one pin and a pull up
resistor. Send you a copy if you like.
/Ake fredrikssonjohan wrote:
> Hi!
>
> Sorry if this is a stupid question, but I haven't found any good info
> about the UART levels so I better ask!
>
> Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is on 5V.
> Can they talk as it is or do I need a 3.3 to 5V buffer between?
>
> Thanks for any help!
>
> Cheers
> /Johan > >. >
>
--
---
Ake Hedman (YAP - Yet Another Programmer)
eurosource, Brattbergavägen 17, 820 50 LOS, Sweden
Phone: (46) 657 413430 Cellular: (46) 73 84 84 102
Company home: http://www.eurosource.se
Kryddor/Te/Kaffe: http://www.brattberg.com
Personal homepage: http://www.eurosource.se/akhe
Automated home: http://www.vscp.org
Yahoo! Groups Links
Regards,
Martin
----- Original Message -----
From: "Ake Hedman, eurosource" <akhe@akhe...>
To: <lpc2000@lpc2...>
Sent: Thursday, November 10, 2005 10:25 PM
Subject: Re: [lpc2000] Is LPC2138 UART levels OK for a 5V part? Not my business but why use the DS-2480? Its code available for
1-Wire/LPC that works perfectly with the use of one pin and a pull up
resistor. Send you a copy if you like.
/Ake fredrikssonjohan wrote:
> Hi!
>
> Sorry if this is a stupid question, but I haven't found any good info
> about the UART levels so I better ask!
>
> Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is on 5V.
> Can they talk as it is or do I need a 3.3 to 5V buffer between?
>
> Thanks for any help!
>
> Cheers
> /Johan > >. >
>
--
---
Ake Hedman (YAP - Yet Another Programmer)
eurosource, Brattbergavägen 17, 820 50 LOS, Sweden
Phone: (46) 657 413430 Cellular: (46) 73 84 84 102
Company home: http://www.eurosource.se
Kryddor/Te/Kaffe: http://www.brattberg.com
Personal homepage: http://www.eurosource.se/akhe
Automated home: http://www.vscp.org
Yahoo! Groups Links
Reply by ●November 11, 20052005-11-11
Hi!
The main reason for using it was because it takes care of timings and
adjust depending on the load of the 1-wire bus.
I use it with a mux and collects data from 8 channels. A normal load
is 32pcs of DS1822 on 180 meter cable. Another example is 1200 sensors
spread over a 3600 meter of cables muxed to 80 channels.
How reliable would you say the bit banged one is when you have bigger
loads and longer lines?
As said in a later reply, please upload to file area if possible!
/Johan
PS. Roligt att trfa pfler fr Svedala h. :-)
--- In lpc2000@lpc2..., "Ake Hedman, eurosource" <akhe@b...>
wrote:
>
> Not my business but why use the DS-2480? Its code available for
> 1-Wire/LPC that works perfectly with the use of one pin and a pull up
> resistor. Send you a copy if you like.
>
> /Ake
The main reason for using it was because it takes care of timings and
adjust depending on the load of the 1-wire bus.
I use it with a mux and collects data from 8 channels. A normal load
is 32pcs of DS1822 on 180 meter cable. Another example is 1200 sensors
spread over a 3600 meter of cables muxed to 80 channels.
How reliable would you say the bit banged one is when you have bigger
loads and longer lines?
As said in a later reply, please upload to file area if possible!
/Johan
PS. Roligt att trfa pfler fr Svedala h. :-)
--- In lpc2000@lpc2..., "Ake Hedman, eurosource" <akhe@b...>
wrote:
>
> Not my business but why use the DS-2480? Its code available for
> 1-Wire/LPC that works perfectly with the use of one pin and a pull up
> resistor. Send you a copy if you like.
>
> /Ake
Reply by ●November 11, 20052005-11-11
I send it directly to you.
/Ake
Martin Maurer wrote:
> Can you upload the code ? Thanks !
>
> Regards,
>
> Martin
>
> ----- Original Message -----
> From: "Ake Hedman, eurosource" <akhe@akhe...>
> To: <lpc2000@lpc2...>
> Sent: Thursday, November 10, 2005 10:25 PM
> Subject: Re: [lpc2000] Is LPC2138 UART levels OK for a 5V part? > Not my business but why use the DS-2480? Its code available for
> 1-Wire/LPC that works perfectly with the use of one pin and a pull up
> resistor. Send you a copy if you like.
>
> /Ake > fredrikssonjohan wrote:
>
> > Hi!
> >
> > Sorry if this is a stupid question, but I haven't found any good info
> > about the UART levels so I better ask!
> >
> > Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is on 5V.
> > Can they talk as it is or do I need a 3.3 to 5V buffer between?
> >
> > Thanks for any help!
> >
> > Cheers
> > /Johan
> >
> >
> >
> >
> >
> > >.
> >
> >
> >
> > --
> ---
> Ake Hedman (YAP - Yet Another Programmer)
> eurosource, Brattbergavägen 17, 820 50 LOS, Sweden
> Phone: (46) 657 413430 Cellular: (46) 73 84 84 102
> Company home: http://www.eurosource.se
> Kryddor/Te/Kaffe: http://www.brattberg.com
> Personal homepage: http://www.eurosource.se/akhe
> Automated home: http://www.vscp.org >
> >. >
>
--
---
Ake Hedman (YAP - Yet Another Programmer)
eurosource, Brattbergavägen 17, 820 50 LOS, Sweden
Phone: (46) 657 413430 Cellular: (46) 73 84 84 102
Company home: http://www.eurosource.se
Kryddor/Te/Kaffe: http://www.brattberg.com
Personal homepage: http://www.eurosource.se/akhe
Automated home: http://www.vscp.org
/Ake
Martin Maurer wrote:
> Can you upload the code ? Thanks !
>
> Regards,
>
> Martin
>
> ----- Original Message -----
> From: "Ake Hedman, eurosource" <akhe@akhe...>
> To: <lpc2000@lpc2...>
> Sent: Thursday, November 10, 2005 10:25 PM
> Subject: Re: [lpc2000] Is LPC2138 UART levels OK for a 5V part? > Not my business but why use the DS-2480? Its code available for
> 1-Wire/LPC that works perfectly with the use of one pin and a pull up
> resistor. Send you a copy if you like.
>
> /Ake > fredrikssonjohan wrote:
>
> > Hi!
> >
> > Sorry if this is a stupid question, but I haven't found any good info
> > about the UART levels so I better ask!
> >
> > Need to connect a LPC2138 to a Maxim (Dallas) DS2480B which is on 5V.
> > Can they talk as it is or do I need a 3.3 to 5V buffer between?
> >
> > Thanks for any help!
> >
> > Cheers
> > /Johan
> >
> >
> >
> >
> >
> > >.
> >
> >
> >
> > --
> ---
> Ake Hedman (YAP - Yet Another Programmer)
> eurosource, Brattbergavägen 17, 820 50 LOS, Sweden
> Phone: (46) 657 413430 Cellular: (46) 73 84 84 102
> Company home: http://www.eurosource.se
> Kryddor/Te/Kaffe: http://www.brattberg.com
> Personal homepage: http://www.eurosource.se/akhe
> Automated home: http://www.vscp.org >
> >. >
>
--
---
Ake Hedman (YAP - Yet Another Programmer)
eurosource, Brattbergavägen 17, 820 50 LOS, Sweden
Phone: (46) 657 413430 Cellular: (46) 73 84 84 102
Company home: http://www.eurosource.se
Kryddor/Te/Kaffe: http://www.brattberg.com
Personal homepage: http://www.eurosource.se/akhe
Automated home: http://www.vscp.org
Reply by ●November 11, 20052005-11-11
Fredrik,
>please upload to file area if possible!
I will do that.
>....1200 sensors...
May I as what you do!?
Cheers
/Ake
fredrikssonjohan wrote:
> Hi!
>
> The main reason for using it was because it takes care of timings and
> adjust depending on the load of the 1-wire bus.
>
> I use it with a mux and collects data from 8 channels. A normal load
> is 32pcs of DS1822 on 180 meter cable. Another example is 1200 sensors
> spread over a 3600 meter of cables muxed to 80 channels.
>
> How reliable would you say the bit banged one is when you have bigger
> loads and longer lines?
>
> As said in a later reply, please upload to file area if possible!
>
> /Johan
>
> PS. Roligt att trfa pfler fr Svedala h. :-)
>
> --- In lpc2000@lpc2..., "Ake Hedman, eurosource" <akhe@b...>
> wrote:
> >
> > Not my business but why use the DS-2480? Its code available for
> > 1-Wire/LPC that works perfectly with the use of one pin and a pull up
> > resistor. Send you a copy if you like.
> >
> > /Ake >
> >. >
>
--
---
Ake Hedman (YAP - Yet Another Programmer)
eurosource, Brattbergavägen 17, 820 50 LOS, Sweden
Phone: (46) 657 413430 Cellular: (46) 73 84 84 102
Company home: http://www.eurosource.se
Kryddor/Te/Kaffe: http://www.brattberg.com
Personal homepage: http://www.eurosource.se/akhe
Automated home: http://www.vscp.org
>please upload to file area if possible!
I will do that.
>....1200 sensors...
May I as what you do!?
Cheers
/Ake
fredrikssonjohan wrote:
> Hi!
>
> The main reason for using it was because it takes care of timings and
> adjust depending on the load of the 1-wire bus.
>
> I use it with a mux and collects data from 8 channels. A normal load
> is 32pcs of DS1822 on 180 meter cable. Another example is 1200 sensors
> spread over a 3600 meter of cables muxed to 80 channels.
>
> How reliable would you say the bit banged one is when you have bigger
> loads and longer lines?
>
> As said in a later reply, please upload to file area if possible!
>
> /Johan
>
> PS. Roligt att trfa pfler fr Svedala h. :-)
>
> --- In lpc2000@lpc2..., "Ake Hedman, eurosource" <akhe@b...>
> wrote:
> >
> > Not my business but why use the DS-2480? Its code available for
> > 1-Wire/LPC that works perfectly with the use of one pin and a pull up
> > resistor. Send you a copy if you like.
> >
> > /Ake >
> >. >
>
--
---
Ake Hedman (YAP - Yet Another Programmer)
eurosource, Brattbergavägen 17, 820 50 LOS, Sweden
Phone: (46) 657 413430 Cellular: (46) 73 84 84 102
Company home: http://www.eurosource.se
Kryddor/Te/Kaffe: http://www.brattberg.com
Personal homepage: http://www.eurosource.se/akhe
Automated home: http://www.vscp.org
