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How can I connect PC to HC11 through RS232?

Started by Alexey Londkevich November 18, 2004
Hello, all.

I am beginner in 68hc11 progamming.
I must make some changes for same program.
I want to write small debug program for debugging through serial connection.
I connect PC directly to 68hc11. (Ground -ground, td-rd, rd-td).
I trying send chars from 68hc11 to PS. It work.
But I can not send char from PC.
What do I wrongly?
Perhaps it is no right - directly connection?





You just can't connect directly to the PC from the HC11. You need to
go thru the RS232. You also need a pull up resistor for the TxD pin
of the HC11. What I usually do is I also used a Sub-D9 connector to
connect to the Serial port of the PC.

-Quyen

--- In , Alexey Londkevich <lond@u...> wrote:
> Hello, all.
>
> I am beginner in 68hc11 progamming.
> I must make some changes for same program.
> I want to write small debug program for debugging through serial
connection.
> I connect PC directly to 68hc11. (Ground -ground, td-rd, rd-td).
> I trying send chars from 68hc11 to PS. It work.
> But I can not send char from PC.
> What do I wrongly?
> Perhaps it is no right - directly connection?



Hello,
You must use a Rs-232 transciver chip such as the MAX232. What this chip does is it translates the voltages from the RX side of the RS232 protocol into Logic-level (+5V) for the MCU to understand. It then translates the TX pin voltage from logic-level to the necessary -13 to 0 voltage level to match the RS232 protocol. It's a bit confusing, but once you get it, you wont forget it. I suggest doing a Google search for "RS-232 protocol" you will find a bunch of information.

I hope this answer was along the lines of what you are looking for. RS-232 is a wonderful protocol with a lot of potential. Take care.

LF Alexey Londkevich <> wrote:
Hello, all.

I am beginner in 68hc11 progamming.
I must make some changes for same program.
I want to write small debug program for debugging through serial connection.
I connect PC directly to 68hc11. (Ground -ground, td-rd, rd-td).
I trying send chars from 68hc11 to PS. It work.
But I can not send char from PC.
What do I wrongly?
Perhaps it is no right - directly connection?

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Hi all and LF,

You are close, but the RS-232 signaling levels are -15 to -5 (low state) and +5 to +15 for a high.

Scott bart homerson <> wrote:

Hello,
You must use a Rs-232 transciver chip such as the MAX232. What this chip does is it translates the voltages from the RX side of the RS232 protocol into Logic-level (+5V) for the MCU to understand. It then translates the TX pin voltage from logic-level to the necessary -13 to 0 voltage level to match the RS232 protocol. It's a bit confusing, but once you get it, you wont forget it. I suggest doing a Google search for "RS-232 protocol" you will find a bunch of information.

I hope this answer was along the lines of what you are looking for. RS-232 is a wonderful protocol with a lot of potential. Take care.

LF Alexey Londkevich wrote:
Hello, all.

I am beginner in 68hc11 progamming.
I must make some changes for same program.
I want to write small debug program for debugging through serial connection.
I connect PC directly to 68hc11. (Ground -ground, td-rd, rd-td).
I trying send chars from 68hc11 to PS. It work.
But I can not send char from PC.
What do I wrongly?
Perhaps it is no right - directly connection?

---------------------------------
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Hello scott,

Actually, the standard says that the voltage can be between +25 and -25. We're both incorrect. Thanks for making me look it up, my memory often fails me.

Quoted from http://www.camiresearch.com/Data_Com_Basics/RS232_standard.html

Signal State Voltage Assignments - Voltages of -3v to -25v with respect to signal ground (pin 7) are considered logic '1' (the marking condition), whereas voltages of +3v to +25v are considered logic '0' (the spacing condition). The range of voltages between -3v and +3v is considered a transition region for which a signal state is not assigned.

I commonly see -13V, but rarely see anything over +5V on the oscilloscope with my configuration.

LF

Scott Grodevant <> wrote:

Hi all and LF,

You are close, but the RS-232 signaling levels are -15 to -5 (low state) and +5 to +15 for a high.

Scott bart homerson wrote:

Hello,
You must use a Rs-232 transciver chip such as the MAX232. What this chip does is it translates the voltages from the RX side of the RS232 protocol into Logic-level (+5V) for the MCU to understand. It then translates the TX pin voltage from logic-level to the necessary -13 to 0 voltage level to match the RS232 protocol. It's a bit confusing, but once you get it, you wont forget it. I suggest doing a Google search for "RS-232 protocol" you will find a bunch of information.

I hope this answer was along the lines of what you are looking for. RS-232 is a wonderful protocol with a lot of potential. Take care.

LF Alexey Londkevich wrote:
Hello, all.

I am beginner in 68hc11 progamming.
I must make some changes for same program.
I want to write small debug program for debugging through serial connection.
I connect PC directly to 68hc11. (Ground -ground, td-rd, rd-td).
I trying send chars from 68hc11 to PS. It work.
But I can not send char from PC.
What do I wrongly?
Perhaps it is no right - directly connection?

---------------------------------
Yahoo! Groups Links

To
---------------------------------
Yahoo! Groups Links
---------------------------------
Yahoo! Groups Links
---------------------------------



Hi all and LF,

Thanks, my memory must be slipping too.

Scott

bart homerson <> wrote:

Hello scott,

Actually, the standard says that the voltage can be between +25 and -25. We're both incorrect. Thanks for making me look it up, my memory often fails me.

Quoted from http://www.camiresearch.com/Data_Com_Basics/RS232_standard.html

Signal State Voltage Assignments - Voltages of -3v to -25v with respect to signal ground (pin 7) are considered logic '1' (the marking condition), whereas voltages of +3v to +25v are considered logic '0' (the spacing condition). The range of voltages between -3v and +3v is considered a transition region for which a signal state is not assigned.

I commonly see -13V, but rarely see anything over +5V on the oscilloscope with my configuration.

LF

Scott Grodevant wrote:

Hi all and LF,

You are close, but the RS-232 signaling levels are -15 to -5 (low state) and +5 to +15 for a high.

Scott bart homerson wrote:

Hello,
You must use a Rs-232 transciver chip such as the MAX232. What this chip does is it translates the voltages from the RX side of the RS232 protocol into Logic-level (+5V) for the MCU to understand. It then translates the TX pin voltage from logic-level to the necessary -13 to 0 voltage level to match the RS232 protocol. It's a bit confusing, but once you get it, you wont forget it. I suggest doing a Google search for "RS-232 protocol" you will find a bunch of information.

I hope this answer was along the lines of what you are looking for. RS-232 is a wonderful protocol with a lot of potential. Take care.

LF Alexey Londkevich wrote:
Hello, all.

I am beginner in 68hc11 progamming.
I must make some changes for same program.
I want to write small debug program for debugging through serial connection.
I connect PC directly to 68hc11. (Ground -ground, td-rd, rd-td).
I trying send chars from 68hc11 to PS. It work.
But I can not send char from PC.
What do I wrongly?
Perhaps it is no right - directly connection?

---------------------------------
Yahoo! Groups Links

To
---------------------------------
Yahoo! Groups Links
---------------------------------
Yahoo! Groups Links
---------------------------------
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---------------------------------



Thanx, people for explainig and links.
Will to try MAX 232




lol

LF

Scott Grodevant <> wrote:

Hi all and LF,

Thanks, my memory must be slipping too.

Scott

bart homerson wrote:

Hello scott,

Actually, the standard says that the voltage can be between +25 and -25. We're both incorrect. Thanks for making me look it up, my memory often fails me.

Quoted from http://www.camiresearch.com/Data_Com_Basics/RS232_standard.html

Signal State Voltage Assignments - Voltages of -3v to -25v with respect to signal ground (pin 7) are considered logic '1' (the marking condition), whereas voltages of +3v to +25v are considered logic '0' (the spacing condition). The range of voltages between -3v and +3v is considered a transition region for which a signal state is not assigned.

I commonly see -13V, but rarely see anything over +5V on the oscilloscope with my configuration.

LF

Scott Grodevant wrote:

Hi all and LF,

You are close, but the RS-232 signaling levels are -15 to -5 (low state) and +5 to +15 for a high.

Scott bart homerson wrote:

Hello,
You must use a Rs-232 transciver chip such as the MAX232. What this chip does is it translates the voltages from the RX side of the RS232 protocol into Logic-level (+5V) for the MCU to understand. It then translates the TX pin voltage from logic-level to the necessary -13 to 0 voltage level to match the RS232 protocol. It's a bit confusing, but once you get it, you wont forget it. I suggest doing a Google search for "RS-232 protocol" you will find a bunch of information.

I hope this answer was along the lines of what you are looking for. RS-232 is a wonderful protocol with a lot of potential. Take care.

LF Alexey Londkevich wrote:
Hello, all.

I am beginner in 68hc11 progamming.
I must make some changes for same program.
I want to write small debug program for debugging through serial connection.
I connect PC directly to 68hc11. (Ground -ground, td-rd, rd-td).
I trying send chars from 68hc11 to PS. It work.
But I can not send char from PC.
What do I wrongly?
Perhaps it is no right - directly connection?

---------------------------------
Yahoo! Groups Links

To
---------------------------------




If you are going to use the MAX 232, then you will need to order some capacitors too. There are RS232 chips that do not require them; the MAX232 was the first chip that came to my mind. I would suggest that you look through the data sheets of the various chips before you actually make a decision. Digikey, http://www.digikey.com, has 1284 different RS232 devices they also usually have a good number of data sheets for the chips they stock. Good luck.

LF
Alexey Londkevich <> wrote:
Thanx, people for explainig and links.
Will to try MAX 232

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Thanx, I will to study this site

On Friday 19 of November 2004 22:39, bart homerson wrote:
> If you are going to use the MAX 232, then you will need to order some
> capacitors too. There are RS232 chips that do not require them; the MAX232
> was the first chip that came to my mind. I would suggest that you look
> through the data sheets of the various chips before you actually make a
> decision. Digikey, http://www.digikey.com, has 1284 different RS232
> devices they also usually have a good number of data sheets for the chips
> they stock. Good luck.
>
> LF >
> Alexey Londkevich <> wrote:
> Thanx, people for explainig and links.
> Will to try MAX 232
>
> Yahoo! Groups Sponsor
> Get unlimited calls to
>
> U.S./Canada > ---------------------------------
> Yahoo! Groups Links
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