What I want to do is to sample a light, and of course I want the highest frequency as possible because I want to write those data in a graph made with python. I'm fairly sure that the buffer gets full after those 22 samples. You want to get the data down the serial port faster, so you can spend a higher percentage of your time in the stupid delay function?
There are only two ways to make that happen. Send the data faster or send less data. Neither seems likely, since you may be using the highest supported baud rate already, and sending binary data may actually result in more data.
PaulS: You want to get the data down the serial port faster, so you can spend a higher percentage of your time in the stupid delay function? I used the first delay to avoid getting immediately inside the while and repress is. The second one has the same function: I use it to not get inside the loop immediately after I told it stop.
This will save between characters per sample. A 0V GND signal represents either a start bit or a data bit of value 0. RS, which can be found on some of the more ancient computers and peripherals, is like TTL serial flipped on its head.
On these signals a low voltage -5V, V, etc. A high RS signal means either a start bit, or a 0-value data bit. That's kind of the opposite of TTL serial. Between the two serial signal standards, TTL is much easier to implement into embedded circuits. However the low voltage levels are more susceptible to losses across long transmission lines.
RS, or more complex standards like RS, are better suited to long range serial transmissions. When you're connecting two serial devices together, it's important to make sure their signal voltages match up. You'll have to shift those signals! Continuing on, we'll explore the tool microcontrollers use to convert their data on a parallel bus to and from a serial interface.
The final piece to this serial puzzle is finding something to both create the serial packets and control those physical hardware lines. Enter the UART. Essentially, the UART acts as an intermediary between parallel and serial interfaces. Super-simplified UART interface. Parallel on one end, serial on the other. You'll have to check your microcontroller's datasheet to see if it has any UARTs.
Some have none, some have one, some have many. On the transmit side, a UART must create the data packet - appending sync and parity bits - and send that packet out the TX line with precise timing according to the set baud rate. On the receive end, the UART has to sample the RX line at rates according to the expected baud rate, pick out the sync bits, and spit out the data. More advanced UARTs may throw their received data into a buffer , where it can stay until the microcontroller comes to get it.
Buffers can be as small as a few bits, or as large as thousands of bytes. If a microcontroller doesn't have a UART or doesn't have enough , the serial interface can be bit-banged - directly controlled by the processor. This is the approach Arduino libraries like SoftwareSerial take. Bit-banging is processor-intensive, and not usually as precise as a UART, but it works in a pinch! I'd like to leave you with a few common mistakes that are easy for an engineer of any experience level to make:.
Seems simple enough, but it's a mistake I know I've made more than a few times. As much as you want their labels to match up, always make sure to cross the RX and TX lines between serial devices.
Note RX and TX's crossed! Contrary to what the esteemed Dr. Egon Spengler would warn , cross the streams. Baud rates are like the languages of serial communication. If two devices aren't speaking at the same speed, data can be either misinterpreted, or completely missed.
If all the receiving device sees on its receive line is garbage, check to make sure the baud rates match up. Data transmitted at bps, but received at bps. Serial communication is designed to allow just two devices to communicate across one serial bus. If more than one device is trying to transmit on the same serial line you could run into bus-contention. Dun dun dun Two transmitters sending to a single receiver sets up the possibility for bus contention.
Two devices trying to transmit data at the same time, on the same line, is bad! At "best" neither of the devices will get to send their data. At worst, both device's transmit lines go poof though that's rare, and usually protected against. It can be safe to connect multiple receiving devices to a single transmitting device. Not really up to spec and probably frowned upon by a hardened engineer, but it'll work. Distributing a TX line like this can still be dangerous from a firmware perspective, because you can't pick and choose which device hears what transmission.
However, equipment comes in the following types, and depending on the equipment that will be connected, a straight cable or a crossover cable is required. Data communication equipment. This term indicates equipment that passively operates such as modems, printers, and plotters. In serial communication, data is sent one bit at a time using one signal line, so in order for the receiving side to accurately receive the data, the sending side must know at what speed it is sending each bit.
In RSC, synchronous communication and asynchronous communication standards have been defined. For peripheral equipment used for measurements or control, the previously mentioned full-duplex communication and asynchronous communication are typically used.
Serial communication standards Signal assignments and connectors Connection method Half-duplex communication and full-duplex communication Asynchronous communication and synchronous communication What is serial communication?
See all RSC communication devices. Otherwise worded: How do I resolve my understanding about baud rates and high speed serial data transfer? From what I understand, serial communication is relatively slow. By slow, I mean that the fastest common rate of transmission of data is However, also from what I understand there are fast ways of transferring data serially. I know that some serial configurations through Firewire or Ethernet can transfer data at speeds that are orders of magnitude higher than These data streams are able to be read on simple computers that you can buy from Staples.
I don't know how these systems receive data at such a high speed if common baud rates are so low. I know something is wrong with my understanding of it all. I am new to electrical engineering and I am trying to teach myself some basic ideas for my research project - with much frustration. I know that I need to have a system that can receive a pulse train at a minimum speed of 10MHz hopefully up to MHz.
I will then program it to process this data. The system that I currently have to receive the data is an Arduino certified product:. Programming in the Arduino language is not a problem, I already know how to do this. I just want to understand what I can do to receive this data stream.
Do I need something faster than this? Or will this suffice? I'm more interested in the theory than the device; it is more valuable for me to bolster my education than for me to solve my problem though it needs to be solved. With asynchronous , which is what serial as in UART and RS are, it's all down to how accurate a system's clock is. Both ends of the line have to agree on the same speed baud rate and any deviation from that causes transmission errors.
The more accurately the two ends can agree on their baud rates the faster you can transfer data. Note that on many systems Arduino included when you ask for one baud rate you actually get a slightly different baud rate. That's due to the way that the internal UART hardware works - it divides the system clock into finer and finer bits to get as close to the requested baud rate as possible.
Lower baud rates are easer to get close to, but higher ones are much harder. So it's "safer" to use a lower baud rate which gives more reliable communication to a greater variety of devices. The other kind of serial, synchronous , uses an extra wire for the transmitting or master end of the connection to send the clock to the receiving slave end.
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