Problems with logic analyzer

[evansg124]

Hello!

I am testing a logic analyzer that I found on amazon from AZ-Delivery with the Salae logic 2 software and I am having some problems.

Here is how it is connected to Serial 1: ( RX1 purple cable does nothing in this case)

I am using this simple code:

void setup() {
  Serial1.begin(115200);
}

void loop() {

  Serial1.print("HELLO");
  delay(2000);

}

The issue that I am having is that if I use a 9600 baudrate the logic analyzer decodes the message perfectly, but if I use 115200 baudrate it gives the following errors when decoding:

What can be the possible issue?

[DrDiettrich]

@evansg124

What can be the possible issue?

You will have to tell the program the baudrate to expect.

[evansg124]

I placed it here. However, I see it says Bit rate and not baudrate I guess they are different things?

[DrDiettrich]

@evansg124

I guess they are different things?

Find out yourself, I can not read the program documentation.

[Paul_KD7HB]

@evansg124

I see it says Bit rate and not baudrate I guess they are different things?

No, they are NOT the same, but most people use them an being the same. Baud rate refers to "flux changes per second", meaning voltage changes per second. Consider a string of identical bits. There are NO changes between bits, The Baud rate counts ONLY the changes.
The bit rate is based on a clock identifying each bit, so a string of identical bits is counted correctly when compared to the clocking pulses.

[anon64005695]

Hello evansg124,
I feel the sampling rate with the high freq is to low. Check the setting in the logic and increase the sampling rate look out for unit MS/s.
Best regards Markus

[DrDiettrich]

@Paul_KD7HB

Baud rate refers to "flux changes per second",

Where did you find that nonsense definition? How would a receiving station then know how many bits are transferred?

[evansg124]

It works perfectly now! Thank you for the solution @anon64005695

[Paul_KD7HB]

That definition has been the case since the first teletype machine was put on line.

[DrDiettrich]

@Paul_KD7HB

That definition has been the case

Only since 15 minutes ago when you posted that nonsense. Please give a link to any document that supports your opinion.

[Paul_KD7HB]

Do you realize that Baud is short for Baudaut, the inventor of wired digital communication. I will look the the definition.

[herbschwarz]

We have some confusion about the subject of baudrate. One problem is that a UART needs a start bit and a stop bit besides the data bits. The protocol is not to be confused with NRZ coding or data bandwidth. Bits per second according to the clock rate is not the same as the data rate. Then there is the problem of using a parity bit that can be added but is not part of the data either. So, maybe baudrate is supposed to relate to the characters sent and not the clock speed.

[DrDiettrich]

@Paul_KD7HB

Baud is short for Baudaut

Look up "Baudot".

@herbschwarz

So, maybe baudrate is supposed to relate to the characters sent and not the clock speed.

That's a meaningful interpretation but not what baudrate means nowadays. The asynchronous transmitter and receiver hardware requires a known bit rate, known as baudrate, and a frame format. Each frame consists of a start bit, a number of data bits, optional parity bit, and at least one stop bit. The number of stop bits does not matter, it was only introduced to slow down the character transmission rate so that mechanical receivers (Teletype...) could advance the chariot after every character.

Likewise the line endings were specified as a sequence of CR and LF, where the Carriage Return started the slow movement of the print head back to the left margin, followed by a quick shift up of the paper (Line Feed) while the print head finishes its movement.

[MrMark]

Baudrate is the rate at which "symbols" are transmitted and bit rate is the rate at which "bits" are transmitted.

Some transmission protocols transmit multiple bits per symbol. For example 4 QAM has 4 states (2 bits) per symbol, 16 QAM has 16 states (4 bits) per symbol. These sorts of things are common in acoustic and RF modems.

Arduino serial ports have two states per symbol (1 bit) so the bit rate and baud rate are the same number with slightly different meanings. In this asynchronous protocol, start bits, message bits, and stop bits are all binary (2 state) "symbols" whose interpretation is position dependent.

[dlloyd]

Baud rate = Bit rate/Number of bits

With baud bit rate = 115200 and transferring 1 start bit + 8 data bits +1 stop bit (10 bits per byte)
bytes / second = baud rate / 10 = 11520

[DrDiettrich]

baud rate = ... baud rate / 10?

The only difference between bitrate and baudrate is the special baud rate sequence, starting at 50 Bd (Teletype), 110 Bd (typewriter) and 300 and binary multiples of it.

[Koepel]

@evansg124 Have you tried sigrok/PulseView ? The Salae software is really good, but sigrok/PulseView is also really good.
A driver "Zadig" is needed for Windows, and you have go guess which driver to use, that is the weird part.

[SteveThackery]

@Paul_KD7HB

That definition has been the case since the first teletype machine was put on line.

Oh no it hasn't! I'm an ex-teletype engineer and spent my career in the telecommunications industry.

Baud rate has nothing whatever to do with flux changes. The baud rate is the symbol rate. With basic serial comms like RS232, each symbol encodes one bit, so the bit rate and baud rate are the same.

With more advanced coding algorithms, each symbol can encode 4, 8, 16 or more bits. In the case of four bits, for example, a bit rate of 1200 bits per second requires 300 symbols per second, so you have a baud rate of 300 and a bit rate of 1200.

Look up QAM for more information.

[SteveThackery]

@herbschwarz

So, maybe baudrate is supposed to relate to the characters sent and not the clock speed.

No. It has nothing whatever to do with stop and start bits, parity bits or anything else. The baud rate refers to the symbol rate.

@DrDiettrich

That's a meaningful interpretation but not what baudrate means nowadays. The asynchronous transmitter and receiver hardware requires a known bit rate, known as baudrate

The rest of what you wrote is correct, but that is completely wrong. The bit rate and baud rate are only the same when the transmission system only encodes one bit per symbol.

@dlloyd

With baud rate = 115200 and transferring 1 start bit + 8 data bits +1 stop bit (10 bits per byte)
bytes / second = baud rate / 10 = 11520

Nonsense.

@DrDiettrich

The only difference between bitrate and baudrate is the special baud rate sequence, starting at 50 Bd (Teletype), 110 Bd (typewriter) and 300 and binary multiples of it.

More nonsense.

Colleagues, I've never read so much misinformation from so-called experts on this forum before. I worked for over 30 years in the telecommunications industry, and I can assure you that bit rate and baud rate are not the same thing, and they have nothing whatever to do with start bits, stop bits, frames, parity bits, or anything else.

The baud rate refers to the number of symbols per second. The bit rate refers to the number of bits per second.

Only in those limited cases where each symbol only encodes one bit (e.g. RS232) are the two numerically equal. All modern transmission systems send multiple bits per symbol, hence the baud rate is lower than the bit rate.

[dlloyd]

@SteveThackery

Nonsense.

EDIT: My apologies ... my example should say 115200 bit rate will transfer 11520 bytes / sec.