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| en:iot-open:embeddedcommunicationprotocols2 [2023/11/18 14:42] – pczekalski | en:iot-open:embeddedcommunicationprotocols2 [2024/03/05 13:43] (current) – pczekalski | ||
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| - | ====== Embedded | + | ====== Embedded |
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| IoT systems and related data flows are typically structured into three primary layers {{ref> | IoT systems and related data flows are typically structured into three primary layers {{ref> | ||
| ((Internet of Things: Architectures, | ((Internet of Things: Architectures, | ||
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| ADC conversion is a process of conversion of the continuous-time signal into a discrete one. It has 2 crucial parameters to consider: | ADC conversion is a process of conversion of the continuous-time signal into a discrete one. It has 2 crucial parameters to consider: | ||
| * Sampling rate: usually measured in Hz (kHz, MHz) is a sampling frequency, or in other words, defines a time period between two consecutive reads. A Nyquist-Shannon theorem defines minimum sampling frequency. Oversampling (using higher than Nyquist-Shannon) is common because many ADC converters built into the MCUs tend to be noisy due to the electromagnetic inference of other components, such as e.g. built-in radio. Oversampling brings the capability to average consecutive reads and obtain more reliable and less noisy ADC conversion. | * Sampling rate: usually measured in Hz (kHz, MHz) is a sampling frequency, or in other words, defines a time period between two consecutive reads. A Nyquist-Shannon theorem defines minimum sampling frequency. Oversampling (using higher than Nyquist-Shannon) is common because many ADC converters built into the MCUs tend to be noisy due to the electromagnetic inference of other components, such as e.g. built-in radio. Oversampling brings the capability to average consecutive reads and obtain more reliable and less noisy ADC conversion. | ||
| - | * Sampling resolution: measured in bits, defines the minimum change in the input voltage the device can measure, | + | * Sampling resolution: measured in bits, defines the minimum change in the input voltage the device can measure, e.g. 12-bit resolution brings 4096 values mapped to the input range. The ideal ADC converter linearly maps the discrete values to the voltage input range. Still, in real-life applications, |
| It is worth noting that each ADC has its useable input range (voltage), and the input and analogue signal should be altered accordingly. In real applications, | It is worth noting that each ADC has its useable input range (voltage), and the input and analogue signal should be altered accordingly. In real applications, | ||
| === Digital === | === Digital === | ||
| - | Simple, true/false information can be processed via digital I/O. Most devices use positive logic, where, | + | Simple, true/false information can be processed via digital I/O. Most devices use positive logic, where, e.g. +5 V (TTL) or +3.3 V (the most popular, yet other voltage standards exist) presents a logical one, also referenced as //HIGH//. In contrast, 0V gives a logical zero, referenced as //LOW//. In real systems, this bounding is fuzzy. It brings some tolerance, simplifying, |
| - | Alternating //HIGH// and //LOW// constitutes a square wave signal, usually used as a clock signal (when symmetrical) or used to control the power delivered to the external devices with means of so-called | + | Alternating //HIGH// and //LOW// constitutes a square wave signal, usually used as a clock signal (when symmetrical) or used to control the power delivered to the external devices with means of so-called PWM. |
| === Communication Protocols === | === Communication Protocols === | ||
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| Asynchronous data transmission does not need any separate synchronization signal, but the transmitter and receiver must use the exact timings, and synchronization information must be included in the information transmitted. Examples of asynchronous interfaces implemented in microcontrollers are 1-Wire and UART (Universal Asynchronous Receiver Transmitter). | Asynchronous data transmission does not need any separate synchronization signal, but the transmitter and receiver must use the exact timings, and synchronization information must be included in the information transmitted. Examples of asynchronous interfaces implemented in microcontrollers are 1-Wire and UART (Universal Asynchronous Receiver Transmitter). | ||
| - | | + | <WRAP excludefrompdf> |
| - | * [[en: | + | Details for selected protocols are presented in the following chapters: |
| - | * [[en: | + | * [[en: |
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| + | </ | ||
