The Wired Connectivity Requirement
As mentioned in the previous topic, a wired protocol is a pre-requisite requirement to communicate with a module that enhances the capability of the application. To illustrate, when communicating with a GSM modem the GSM modem does enable GSM communication or a TCP/IP link to the internet.
The layout requires a sequence of elements that work together to pass the commands and data from the microcontroller to the module.
- The MCU's compliant peripheral initiates the communication with the module, and it will use one of the options available for example I2C
- The wired communication protocol facilitates the data and the commands to the module
- The module utilizes the interaction to either send or receive data
- The wired communication protocol facilitates the return of data or information to the MCU
- The MCU's compliant peripheral receives the data and passes it on
Wired protocols have two options, point-to-point and addressable where a number of nodes may be connected to the MCU's compliant peripheral. The protocol would determine the number of nodes that can be connected.
The choice of the wired protocol may be limited by the interface available, and the speed and number of devices will be limited to the protocol specification.
RS232 would be an example of a wired communications topology where there is no address, so it is point-to-point. RS422/RS485 extends that capability with addressable nodes. RS422/RS485 however is usually used to extend the communications link off-board to adjacent nodes in a daisy chain-styled topology.
The advantage of the list of protocols listed below is that they can be addressed, which means that the MCU can connect to multiple devices or modules.
In the following sections, we will review the various protocol options and how each one can be used to enhance the capabilities of the MCU.
