Could I transmit data through IR without needing to modulate the signal?
Sending serial pulses to the IR LED and receive it through an IR photo detector with some additional circuit such as comparator.
Yes.
But in this case you cannot use sensors that require 'Carrier
frequency".
1 Like
The basic reason for modulation is to mitigate the effects of interfering light signals such as LED bulbs, computer and TV monitors, fluorescent and incandescent lights as well as static IR sources.
Without modulation you would need to somehow cope with the interference possibly with extra filters and signal processing. So you may be able to go short distances with low data rates.
1 Like
Thanks for your support.
I initially planned to avoid modulation because I want to send and receive UART signals. However, upon further research, I discovered irDA devices like the MAX3120 that can convert TTL to IR-modulated signals. While the MAX3120 seems promising, the application note lacks detailed information. Can you advise on achieving a high baud rate with such an irDA device?
You can send UART with modulation.
irDA is only good for 1 to 2 meters.
1 Like
Not reliably in uncontrolled environments, because of very large variations in IR background.
The main purpose of the carrier signal is to allow the background noise to be subtracted.
1 Like
In my application I only want to send UART data through IR (distance is less than 1m).
The block diagram of the MAX3120 shows that TX path is like a switch, meaning that it does not use modulated IR signal, is this correct?
No. Both the carrier signal and pulse modulation are provided by the MCU that drives the switch. The carrier signal frequency has to match the bandpass filter built into the IC. There are many different IrDA standards.
Not sure if this is correct or not, but in the application note you can see that the UART is somehow connected to the irDA without modulation.
Yes that is correct.
IrDA has avery limited distance and baud rate.
As I previously mentioned you can send serial data on a modulated signal
How can i send UART with modulated signals at high data rate? According my knowledge the maximum achievable data rate will be approx. 4800 bps in case of using modulated signal.
How high do you need? It just may not be possible
Maximum 115200 bps. Is this rate achievable by IR?
The MAX3120 will do it.
Does it require an IR encoder/decoder? This info is not mentioned, but I assume that it is required before the input stage.
First let me say I have never used that IC.
It was designed for irDA, so it should have an irDA encoder/decoder but I don't see why it would not work with a standard serial data signal.
Exactly what is you application? There may be other ways to do this
1 Like
This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.