hi, i am trying to connect rf module with 8051. i have connected rf module using UART. i have transmitted and received the data but am not able to compare it with stored value at the receiver end. Also there is some voltage drop in the receiver output as soon as i connect the Rx pin to the reciever module. Can anyone help?? thnaks.
Look at the information you've provided:
- you haven't said what specific "8051" chip you're using;
- you haven't said what RF module you're using;
- you haven't given any details of how you connected them;
- you haven't given any details of why you are "not able to compare";
- you haven't explained what voltage you are actually measuring.
Do you really think that anyone can help based solely on the information that you provided?
Remember: nobody knows anything about you or your project other than what you clearly and explicitly state in your post!
well i am using 89v51rd2 controller.
i am using UART.. that means i am using Tx pin to send the data to the transmitter and Rx pin to get the data from receiver.
Receiver is RX431a module working on 433 Mhz.
When i connect the data received at the receiver to the CRO i get 4.9V and the bits i have sent means i get the expected output. I am sending 'aa' i.e. 1010.....
when i connect the Rx pin and check the voltage it is around 3V so i think controller might not read the logic 1 (high) state.
so is some sort of buffer do i need?
I have already stored 'aa' at the receiver side and the only thing i want to do is to compare this stored value to the value i am transmitting and if they are equal perform some operation like and ID.
I hope this would be sufficient.
is the above TTL or RS232 ?
Erik
Change that to: Is it RS232 or 5V logic level or 3.3V logic level or something else?
In the data sheet they say the output is capable of driving one TTL or one CMOS load but basically it is CMOS compatible. As the controller is TTL therotically it should be able to give the ouput of nearly 5V. But definitely it is not RS232 and i think we won't need a MAX 232 for this.
"As the controller is TTL therotically it should be able to give the ouput of nearly 5V."
Take a closer look at the datasheets for TTL logic. Why do you think TTL logic gates may accept 2.4V as a high level for the inputs, if the TTL outputs reaches nearly 5V? It's the CMOS logic that has almost full swing between GND and VCC.
Few chips in use now are TTL, so it is a term that should be avoided unless it really do mean the TTL technology. The generic term is logic-level. And there is always a need to complement "logic-level" with the full set of voltage parameters. Worst-case low and high output levels, and min required low and high input levels. Since almost everything are CMOS these days, inputs normally doesn't consume a static current - the current drive of outputs are normally only needed to charge/discharge capacitances during transitions.
You say "the datasheet". It is important that you are clear about when you are talking about the processor side, and when you are talking about the radio module side. And how about posting links to "the datasheet"?
None of this has anything to do with Keil!
We are discussing hardware issues here - and that is hard to do without a schematic diagram of the system - aka "circuit diagram"
This forum doesn't support posting images - another reason why this is not a great place for such discussions!
You might be better to go to http://www.8052.com/forum If you do, be sure to give a full & clear description of what you are trying to achieve, what you are using, what you have done so far, and what problems you are having. Give a link to this thread, and also update this thread with a link. Show your schematic. Include links to your datasheets. etc...
Few chips in use now are TTL, so it is a term that should be avoided unless it really do mean the TTL technology. nevertheless that is the term that is prevalent in datasheets for such.
anyhow 'TTL' is levels compatible with both 5V and 3V3 CMOS
When people who write datasheets are wrong, we shouldn't redefine the use as correct but instead insist on using correct definitions. Someday, the people who do write the incorrect datasheets might possibly learn that TTL is a very specific term for a specific concept involving bipolar transistors and with totem-pole outputs that can't get near the VCC rail.