Writing a serial protocol

Through the SPI protocol, devices communicate with each other using master-slave architecture. Although multiple slave devices can be supported by SPI, the number of master devices is limited to one. SPI is known as four-wire serial bus because it consists of four signals:. In full duplex mode, data rates over 1Mbps can be achieved - this is one of the main advantages of the SPI bus.

Compared to I2C, SPI also supports using simple hardware interfacing and provides a higher throughput. However, the SPI protocol also has some drawbacks — the lack of error-checking mechanism and slave acknowledgment feature are some of the major disadvantages. You can probably find a dozen USB cables and connectors lying around in your home.

Originally developed in the s, it was intended to standardize the connection of a number of peripheral devices to a computer. When a device communicates with another device through USB protocol, data travels in the form of packets. All the data packets are composed of 8-bit bytes or multiples of 8-bit bytes, depending on the supported bitrate , where the LSB or Least Significant Bit is transmitted first. If you are building an embedded system that involves USB, make sure you use a USB protocol analyzer to monitor the data on the bus.

Total Phases offers products that support all of the above listed protocols. Click below if you would like to learn more, or have a personal demo designed to specifically address your needs. Total Phase. Register Login. Post Detail. In digital communication, there are two types of data transfer: Serial Communication Parallel Communication To keep things simple, we will focus this article on the basics of serial communication protocols.

Serial Communication In serial communication, the data bits are transmitted one at a time in a sequential manner over the data bus or communication channel. In order to understand this properly, let us consider this situation: Imagine you are shooting at a target with a bow and arrow. Create a free Team What is Teams? Learn more. Asked 3 years, 2 months ago. Active 3 years, 1 month ago. Viewed times. Thanks for contacting me.

Improve this question. Olivier Olivier 3 1 1 bronze badge. Add a comment. Active Oldest Votes. Improve this answer. Thank you for your answer, very clear and very helpful. Based on it I will use both of your suggestions : 1 Test first before write.

But you get it! I checked, the HardwareSerial. Is it in the Arduino Sketch itself or in some. Does it improve performances or not? Have all the TX buffers the same size? Or shall I adjust each? Thank you in advance. I believe they are all the same size. You want to place the define at the top of the HardwareSerial. If you change the TX buffer size, please note that it should be a power of two. Creating a full fledged ASN. It's probably better to keep just the TLV structure. TLV basically consists of three elements: a tag, a length and a value field.

The tag defines the type of the data text string, octet string, integer etc. In ASN. The two integer encodings together make up the value of the sequence. You can also use indefinite length in BER which will allow you to stream data.

In that case you do need to parse your tree correctly though. I'd consider it an advanced topic, you need to know about breadth first and depth first parsing, for one. Using a TLV scheme basically allows you to think of any kind of data structure and encode it. Probably the best well known ASN. If not, you've got the basics covered. Your commands can be created and read by both humans and machines which is a big plus.

You might add a checksum to detect a mal-formed command or one damaged in transit, especially if your channel includes long cable or a radio link. If you need industrial strength your device mustn't cause or allow someone to get hurt or die; you need high data rates, fault recovery, missing packet detection etc. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

Create a free Team What is Teams? Learn more. Asked 7 years, 4 months ago. Active 5 years, 3 months ago. Viewed 23k times. Improve this question. Jeremy Gillick. Jeremy Gillick Jeremy Gillick 1 1 gold badge 3 3 silver badges 8 8 bronze badges. Add a comment. Active Oldest Votes. Start of message The problem with just having end of message is that you don't know what other bytes have already been received when you send your message.

Escape Characters It could be that the checksum adds to a control character, such as the 'start of message' or 'end of message' byte, or the message contains a value equal to a control character. Length Often in binary protocols you see a length byte which tells the receiving device how many characters are in the message. Arduino specific When coming up with a protocol for Arduino the first consideration is how reliable is the communications channel.

Improve this answer. Isn't it possible that the garbage ahead of the real start of message code could contain a start of message control code? How would you deal with this? CMCDragonkai Yes this is a possibility, especially for single byte control codes. However if you encounter a start control code halfway through parsing a message, the message is discarded and parsing restarts.