UARTs and serial port comunication
Started by ●April 16, 2005
Hi everybody!
I am using an RCM3700 and I have a doubt about its serial comunication capabilities:
I mean, I can connect directly to my RCM an I2C device, such an ADC, and a RS232 (5V,
not +-12 of course) without any interface chip, right?
But if I have a 1-wire device, it cannot be made? I need to use a 1-wire to serial interface
chip, such as Dallas DS2480. Still right?
On the datasheet of this ic, it says that it can be connected directly to a RS232 5V device
(my RCM!) or to a UART.
Here comes my big question: does the rabbitcore RCM3700 ( or any other rabbit micro)
have a UART? Or is the processor that is supposed to have one? I have a big confusion
about this matter, can anybody explain me better, or where I am wrong?
For example, how does the rcm connect to the pc by the programming cable, if the Pc's
RS232C is supposed to be +-12V? Does it work at 5V?
Sorry for all these questions, but I hope that someone can help me to clarify it...
Thanks since now, cheers,
Cirutech
Reply by ●April 16, 20052005-04-16
Cirutech,
I certainly have not used an RCM 3700, neither a
dallas DS2480. However, I have used an RCM 3100.
Since I am not familiar with this dallas chip, I will
take your word for it (regading that you want to
interface with an rs-232 chip).
the core module family contains no RS-232 driver chip.
These are only on the SDK. if you wish to
commnuicate with rs-232 you will need a driver chip
for rs-232. then you can connect your UART(TTL)from
rabbit to the UART(RS-232 CHIP). then the output of
this chip will have rs-232 communication
I hope this helps
rob
--- cirutech <cirutech@ciru...> wrote:
>
> Hi everybody!
> I am using an RCM3700 and I have a doubt about its
> serial comunication capabilities:
> I mean, I can connect directly to my RCM an I2C
> device, such an ADC, and a RS232 (5V,
> not +-12 of course) without any interface chip,
> right?
> But if I have a 1-wire device, it cannot be made? I
> need to use a 1-wire to serial interface
> chip, such as Dallas DS2480. Still right?
> On the datasheet of this ic, it says that it can be
> connected directly to a RS232 5V device
> (my RCM!) or to a UART.
>
> Here comes my big question: does the rabbitcore
> RCM3700 ( or any other rabbit micro)
> have a UART? Or is the processor that is supposed
> to have one? I have a big confusion
> about this matter, can anybody explain me better,
> or where I am wrong?
> For example, how does the rcm connect to the pc by
> the programming cable, if the Pc's
> RS232C is supposed to be +-12V? Does it work at 5V?
>
> Sorry for all these questions, but I hope that
> someone can help me to clarify it...
>
> Thanks since now, cheers,
>
> Cirutech >
>
Send instant messages to your online friends http://uk.messenger.yahoo.com
I certainly have not used an RCM 3700, neither a
dallas DS2480. However, I have used an RCM 3100.
Since I am not familiar with this dallas chip, I will
take your word for it (regading that you want to
interface with an rs-232 chip).
the core module family contains no RS-232 driver chip.
These are only on the SDK. if you wish to
commnuicate with rs-232 you will need a driver chip
for rs-232. then you can connect your UART(TTL)from
rabbit to the UART(RS-232 CHIP). then the output of
this chip will have rs-232 communication
I hope this helps
rob
--- cirutech <cirutech@ciru...> wrote:
>
> Hi everybody!
> I am using an RCM3700 and I have a doubt about its
> serial comunication capabilities:
> I mean, I can connect directly to my RCM an I2C
> device, such an ADC, and a RS232 (5V,
> not +-12 of course) without any interface chip,
> right?
> But if I have a 1-wire device, it cannot be made? I
> need to use a 1-wire to serial interface
> chip, such as Dallas DS2480. Still right?
> On the datasheet of this ic, it says that it can be
> connected directly to a RS232 5V device
> (my RCM!) or to a UART.
>
> Here comes my big question: does the rabbitcore
> RCM3700 ( or any other rabbit micro)
> have a UART? Or is the processor that is supposed
> to have one? I have a big confusion
> about this matter, can anybody explain me better,
> or where I am wrong?
> For example, how does the rcm connect to the pc by
> the programming cable, if the Pc's
> RS232C is supposed to be +-12V? Does it work at 5V?
>
> Sorry for all these questions, but I hope that
> someone can help me to clarify it...
>
> Thanks since now, cheers,
>
> Cirutech >
>
Send instant messages to your online friends http://uk.messenger.yahoo.com
Reply by ●April 16, 20052005-04-16
Its all in the manual. Read it first, then come ask about something you
don't understand.
cirutech <c...@libero.it> wrote:
Hi everybody!
I am using an RCM3700 and I have a doubt about its serial comunication capabilities:
I mean, I can connect directly to my RCM an I2C device, such an ADC, and a RS232 (5V,
not +-12 of course) without any interface chip, right?
But if I have a 1-wire device, it cannot be made? I need to use a 1-wire to serial interface
chip, such as Dallas DS2480. Still right?
On the datasheet of this ic, it says that it can be connected directly to a RS232 5V device
(my RCM!) or to a UART.
Here comes my big question: does the rabbitcore RCM3700 ( or any other rabbit micro)
have a UART? Or is the processor that is supposed to have one? I have a big confusion
about this matter, can anybody explain me better, or where I am wrong?
For example, how does the rcm connect to the pc by the programming cable, if the Pc's
RS232C is supposed to be +-12V? Does it work at 5V?
Sorry for all these questions, but I hope that someone can help me to clarify it...
Thanks since now, cheers,
Cirutech
Reply by ●April 18, 20052005-04-18
Hi again!
steve was right: I read again all the rcm3700 manual, and I understood
what I am missing: the difference between a serial port and an UART.
I know this is a not-so-little-question, but reading the manual I
found all about the serial ports,nothing about an UART.
In the first answer to my previous post, it was written:
"if you wish to commnuicate with rs-232 you will need a driver chip
for rs-232. then you can connect your UART(TTL)from
rabbit to the UART(RS-232 CHIP). then the output of
this chip will have rs-232 communication"
So it is supposed to intend that the serial output of my rcm core is
an UART? But it's CMOS, as the RCM 3100, not ttl. But it isn't this
the point ( a level translator and this is fixed), it's the UART that
I cannot understand..
So, hoping that this post will be more clear, and hoping that anybody
ca help me, all the best,
Cirutech
--- In rabbit-semi@rabb..., Steve Trigero <seecwriter@y...> wrote:
> Its all in the manual. Read it first, then come ask about something
you don't understand.
>
>
Reply by ●April 18, 20052005-04-18
The point that the poster was trying to make was that
the serial output of the rabbit is a digital signal
(0-3.3v), not RS-232 voltage levels (-10v to +10v).
You will need to connect the serial port signals to a
RS-232 transceiver to get true RS-232 levels.
Something like a MAX232.
Terms "UART" and "serial port" mean the same thing.
All serial ports use a UART. When you call the serial
port initialization procedures you are configuring the
UART (a.k.a, serial port) to operate as you specify in
the call.
Steve --- cirutech <cirutech@ciru...> wrote:
>
> Hi again!
> steve was right: I read again all the rcm3700
> manual, and I understood
> what I am missing: the difference between a serial
> port and an UART.
> I know this is a not-so-little-question, but reading
> the manual I
> found all about the serial ports,nothing about an
> UART.
> In the first answer to my previous post, it was
> written:
> "if you wish to commnuicate with rs-232 you will
> need a driver chip
> for rs-232. then you can connect your UART(TTL)from
> rabbit to the UART(RS-232 CHIP). then the output of
> this chip will have rs-232 communication"
> So it is supposed to intend that the serial output
> of my rcm core is
> an UART? But it's CMOS, as the RCM 3100, not ttl.
> But it isn't this
> the point ( a level translator and this is fixed),
> it's the UART that
> I cannot understand..
>
> So, hoping that this post will be more clear, and
> hoping that anybody
> ca help me, all the best,
>
> Cirutech >
>
> --- In rabbit-semi@rabb..., Steve Trigero
> <seecwriter@y...> wrote:
> > Its all in the manual. Read it first, then come
> ask about something
> you don't understand.
> >
the serial output of the rabbit is a digital signal
(0-3.3v), not RS-232 voltage levels (-10v to +10v).
You will need to connect the serial port signals to a
RS-232 transceiver to get true RS-232 levels.
Something like a MAX232.
Terms "UART" and "serial port" mean the same thing.
All serial ports use a UART. When you call the serial
port initialization procedures you are configuring the
UART (a.k.a, serial port) to operate as you specify in
the call.
Steve --- cirutech <cirutech@ciru...> wrote:
>
> Hi again!
> steve was right: I read again all the rcm3700
> manual, and I understood
> what I am missing: the difference between a serial
> port and an UART.
> I know this is a not-so-little-question, but reading
> the manual I
> found all about the serial ports,nothing about an
> UART.
> In the first answer to my previous post, it was
> written:
> "if you wish to commnuicate with rs-232 you will
> need a driver chip
> for rs-232. then you can connect your UART(TTL)from
> rabbit to the UART(RS-232 CHIP). then the output of
> this chip will have rs-232 communication"
> So it is supposed to intend that the serial output
> of my rcm core is
> an UART? But it's CMOS, as the RCM 3100, not ttl.
> But it isn't this
> the point ( a level translator and this is fixed),
> it's the UART that
> I cannot understand..
>
> So, hoping that this post will be more clear, and
> hoping that anybody
> ca help me, all the best,
>
> Cirutech >
>
> --- In rabbit-semi@rabb..., Steve Trigero
> <seecwriter@y...> wrote:
> > Its all in the manual. Read it first, then come
> ask about something
> you don't understand.
> >
Reply by ●April 18, 20052005-04-18
I think a little further explanation might help.....
UART means... Universal
Asynchronous
Receive &
Transmit
This is simply a serial communications chip. These are the heart of any kind of serial communications, be it RS232/RS422/RS485....etc.
RS232 is an electrical specification...NOT A CHIP. RS232 can be acheived by utilizing a level shifter chip to convert the 0 to 5v levels of the UART output to +/- 10v levels for RS232. There are as many electrical specs as there are types of UARTs too..... RS232/422/485. All of them common, all of them electrical specs.
mark >
> The point that the poster was trying to make was that
> the serial output of the rabbit is a digital signal
> (0-3.3v), not RS-232 voltage levels (-10v to +10v).
> You will need to connect the serial port signals to a
> RS-232 transceiver to get true RS-232 levels.
> Something like a MAX232.
>
> Terms "UART" and "serial port" mean the same thing.
> All serial ports use a UART. When you call the serial
> port initialization procedures you are configuring the
> UART (a.k.a, serial port) to operate as you specify in
> the call.
>
> Steve > --- cirutech <cirutech@ciru...> wrote:
> >
> > Hi again!
> > steve was right: I read again all the rcm3700
> > manual, and I understood
> > what I am missing: the difference between a serial
> > port and an UART.
> > I know this is a not-so-little-question, but reading
> > the manual I
> > found all about the serial ports,nothing about an
> > UART.
> > In the first answer to my previous post, it was
> > written:
> > "if you wish to commnuicate with rs-232 you will
> > need a driver chip
> > for rs-232. then you can connect your UART(TTL)from
> > rabbit to the UART(RS-232 CHIP). then the output of
> > this chip will have rs-232 communication"
> > So it is supposed to intend that the serial output
> > of my rcm core is
> > an UART? But it's CMOS, as the RCM 3100, not ttl.
> > But it isn't this
> > the point ( a level translator and this is fixed),
> > it's the UART that
> > I cannot understand..
> >
> > So, hoping that this post will be more clear, and
> > hoping that anybody
> > ca help me, all the best,
> >
> > Cirutech
> >
> >
> >
> >
> > --- In rabbit-semi@rabb..., Steve Trigero
> > <seecwriter@y...> wrote:
> > > Its all in the manual. Read it first, then come
> > ask about something
> > you don't understand.
> > >
>
> Yahoo! Groups Links >
>
UART means... Universal
Asynchronous
Receive &
Transmit
This is simply a serial communications chip. These are the heart of any kind of serial communications, be it RS232/RS422/RS485....etc.
RS232 is an electrical specification...NOT A CHIP. RS232 can be acheived by utilizing a level shifter chip to convert the 0 to 5v levels of the UART output to +/- 10v levels for RS232. There are as many electrical specs as there are types of UARTs too..... RS232/422/485. All of them common, all of them electrical specs.
mark >
> The point that the poster was trying to make was that
> the serial output of the rabbit is a digital signal
> (0-3.3v), not RS-232 voltage levels (-10v to +10v).
> You will need to connect the serial port signals to a
> RS-232 transceiver to get true RS-232 levels.
> Something like a MAX232.
>
> Terms "UART" and "serial port" mean the same thing.
> All serial ports use a UART. When you call the serial
> port initialization procedures you are configuring the
> UART (a.k.a, serial port) to operate as you specify in
> the call.
>
> Steve > --- cirutech <cirutech@ciru...> wrote:
> >
> > Hi again!
> > steve was right: I read again all the rcm3700
> > manual, and I understood
> > what I am missing: the difference between a serial
> > port and an UART.
> > I know this is a not-so-little-question, but reading
> > the manual I
> > found all about the serial ports,nothing about an
> > UART.
> > In the first answer to my previous post, it was
> > written:
> > "if you wish to commnuicate with rs-232 you will
> > need a driver chip
> > for rs-232. then you can connect your UART(TTL)from
> > rabbit to the UART(RS-232 CHIP). then the output of
> > this chip will have rs-232 communication"
> > So it is supposed to intend that the serial output
> > of my rcm core is
> > an UART? But it's CMOS, as the RCM 3100, not ttl.
> > But it isn't this
> > the point ( a level translator and this is fixed),
> > it's the UART that
> > I cannot understand..
> >
> > So, hoping that this post will be more clear, and
> > hoping that anybody
> > ca help me, all the best,
> >
> > Cirutech
> >
> >
> >
> >
> > --- In rabbit-semi@rabb..., Steve Trigero
> > <seecwriter@y...> wrote:
> > > Its all in the manual. Read it first, then come
> > ask about something
> > you don't understand.
> > >
>
> Yahoo! Groups Links >
>
Reply by ●April 18, 20052005-04-18
At 04:11 PM 4/18/2005 +0000, you wrote:
>So, hoping that this post will be more clear, and hoping that anybody
>ca help me, all the best,
The RS232 chip is just a level converter, it has no brains at
all. Basically if you feed it 3.3/5v (high) the output is -10v. If you
feed it 0, the output is +10v. Coming back the other direction works the same.
The UART is the hardware implementation of the serial shift register that
allows a parallel byte to be transmitted serially, and receive a serially
transmitted byte in a parallel register. The UART also takes care of
"framing", that is the start and stop bits, and optionally, the parity
bit. It also sometimes has a buffer that stores a byte or more, so you
don't have to immediately clear the incoming byte as soon as it is received.
The Rabbit has UART hardware built into it. It's output is TTL level. You
need the chip to shift it to RS232 levels.
On some microprocessors without a UART, you would need to do something
called "bitbanging" where you have to manually toggle a line high and low
to simulate the function of the UART.
For more info, google for "8250 UART" which will tell you more than you
ever want to know.
-Mike
>So, hoping that this post will be more clear, and hoping that anybody
>ca help me, all the best,
The RS232 chip is just a level converter, it has no brains at
all. Basically if you feed it 3.3/5v (high) the output is -10v. If you
feed it 0, the output is +10v. Coming back the other direction works the same.
The UART is the hardware implementation of the serial shift register that
allows a parallel byte to be transmitted serially, and receive a serially
transmitted byte in a parallel register. The UART also takes care of
"framing", that is the start and stop bits, and optionally, the parity
bit. It also sometimes has a buffer that stores a byte or more, so you
don't have to immediately clear the incoming byte as soon as it is received.
The Rabbit has UART hardware built into it. It's output is TTL level. You
need the chip to shift it to RS232 levels.
On some microprocessors without a UART, you would need to do something
called "bitbanging" where you have to manually toggle a line high and low
to simulate the function of the UART.
For more info, google for "8250 UART" which will tell you more than you
ever want to know.
-Mike
Reply by ●April 19, 20052005-04-19
