LED display control
For microcontrollers with a small number of I / O ports, typical parallel-control multi-bit LED 7-segment displays are completely unacceptable. Remote displays in a multichannel system "eat up" almost all the I / O resources of the microcontroller, even when using serial data transmission. Although there are specialized chips oriented on similar tasks (such as the MAX7219 / MAX7221), but a two-digit indication using them is “money down the drain”.
Below is a simple technical solution to the problem. A shift register is used to control the indicator segments, and the selection of the familiarity is made via the data line of the interface. The software component, in this case, is not at all larger than the known methods.
Two transistor switches, connected in series and controlled by an SD interface line, generate antiphase signals. After loading the shift register with the frequency of updating the display data, the log level is set on the SD line. 0 or log. 1 to indicate the corresponding familiarity (Fig.2). With the same success, the CLK interface signal line can also be used for switching, however, the proposed option is more convenient for software implementation of group control of displays with a common CLK line. The length of the control interface can reach tens of meters, and the "twisted pair" ensures reliable transmission. Very convenient local power supply module display type "charger for sotik." It is less efficient, but also easy to manage 2N-bit displays (Fig. 3).
')
The control algorithm is simple. As soon as the data is updated, the state of the SD line is analyzed and the source (s) of the data (low or high) is selected, the serial transfer routine is called and, upon completion, the current state of the SD port is inverted. It is not much more difficult to output a three-digit number with a comma (temperature) on a two-digit indicator.
For an example, a diagram of a module is given, which additionally has an optothyristor control channel.
When using high brightness indicators, transistor switches are not needed.
The display module with the described control method is applicable for modding the computer system unit to display the processor load and temperature inside the case.
PS Please do not kick, the first time I publish an article
PSS The author of this invention is my father. Those. I act as a link between him and the global web.
Below is a simple technical solution to the problem. A shift register is used to control the indicator segments, and the selection of the familiarity is made via the data line of the interface. The software component, in this case, is not at all larger than the known methods.
Two transistor switches, connected in series and controlled by an SD interface line, generate antiphase signals. After loading the shift register with the frequency of updating the display data, the log level is set on the SD line. 0 or log. 1 to indicate the corresponding familiarity (Fig.2). With the same success, the CLK interface signal line can also be used for switching, however, the proposed option is more convenient for software implementation of group control of displays with a common CLK line. The length of the control interface can reach tens of meters, and the "twisted pair" ensures reliable transmission. Very convenient local power supply module display type "charger for sotik." It is less efficient, but also easy to manage 2N-bit displays (Fig. 3).
')
Work logic
The control algorithm is simple. As soon as the data is updated, the state of the SD line is analyzed and the source (s) of the data (low or high) is selected, the serial transfer routine is called and, upon completion, the current state of the SD port is inverted. It is not much more difficult to output a three-digit number with a comma (temperature) on a two-digit indicator.
For an example, a diagram of a module is given, which additionally has an optothyristor control channel.
Options
When using high brightness indicators, transistor switches are not needed.
Practical use
The display module with the described control method is applicable for modding the computer system unit to display the processor load and temperature inside the case.
PS Please do not kick, the first time I publish an article
PSS The author of this invention is my father. Those. I act as a link between him and the global web.
Source: https://habr.com/ru/post/80112/
All Articles