RS232 Expander
Description: I got a problem with my notebook because it has only COM1. My programmer board, Easy-Downloader, must use a serial port, and the application board also needs to communicate via the same serial port. I do remember I have to swap the DB9 connector of both devices many times. So I spent 30 minutes building a simple hardware solution. Of course, it was not an expander by definition, but it helps me a lot. Someone may prefer to call it an RS232 selector, but I like "expander." The above picture is the sample board; no need to make a PCB.
The described circuit addresses the challenge of limited serial port availability on a notebook computer, specifically when two devices need to share a single COM port. The solution involves a simple hardware setup that allows for the swapping of connections between a programmer board (Easy-Downloader) and an application board, both of which utilize the RS232 communication protocol through a DB9 connector.
The circuit can be conceptualized as an RS232 switch or selector. It consists of a DB9 connector for the notebook's COM port, two additional DB9 connectors for the programmer and application boards, and a manual switching mechanism, which can be implemented using a rotary switch or a simple toggle switch. The switch enables the user to select which device is connected to the COM port at any given time, effectively allowing for the sharing of the serial port without the need for physical reconnection.
Wiring for the DB9 connectors should follow standard RS232 pinouts, ensuring that the transmit (TX), receive (RX), and ground (GND) lines are correctly connected. The switch should be wired to connect the appropriate pins from the selected device to the COM port. For example, when the programmer board is selected, the TX pin of the programmer board connects to the RX pin of the notebook, and the RX pin of the programmer board connects to the TX pin of the notebook.
This simple hardware solution is efficient for applications where only one device requires communication at a time, reducing wear on connectors and saving time during device swaps. Additionally, it eliminates the need for a more complex PCB design, making it an accessible option for users with basic electronic assembly skills.I got a problem with my notebook, because it has only COM1. My programmer board, Easy-Downloader must use serial port and the application board also needs to communicate via the same serial port. I do remembered I have to swap DB9 connector of both devices many times. So I spent 30 minutes built above simple hardware. Of course it was not the expander by meaning. But it helps me a lot. Someone may prefer to call it as the rs232 selector, but I like "expander". Above picture is the sample board, no need to make a pcb.
The described circuit addresses the challenge of limited serial port availability on a notebook computer, specifically when two devices need to share a single COM port. The solution involves a simple hardware setup that allows for the swapping of connections between a programmer board (Easy-Downloader) and an application board, both of which utilize the RS232 communication protocol through a DB9 connector.
The circuit can be conceptualized as an RS232 switch or selector. It consists of a DB9 connector for the notebook's COM port, two additional DB9 connectors for the programmer and application boards, and a manual switching mechanism, which can be implemented using a rotary switch or a simple toggle switch. The switch enables the user to select which device is connected to the COM port at any given time, effectively allowing for the sharing of the serial port without the need for physical reconnection.
Wiring for the DB9 connectors should follow standard RS232 pinouts, ensuring that the transmit (TX), receive (RX), and ground (GND) lines are correctly connected. The switch should be wired to connect the appropriate pins from the selected device to the COM port. For example, when the programmer board is selected, the TX pin of the programmer board connects to the RX pin of the notebook, and the RX pin of the programmer board connects to the TX pin of the notebook.
This simple hardware solution is efficient for applications where only one device requires communication at a time, reducing wear on connectors and saving time during device swaps. Additionally, it eliminates the need for a more complex PCB design, making it an accessible option for users with basic electronic assembly skills.I got a problem with my notebook, because it has only COM1. My programmer board, Easy-Downloader must use serial port and the application board also needs to communicate via the same serial port. I do remembered I have to swap DB9 connector of both devices many times. So I spent 30 minutes built above simple hardware. Of course it was not the expander by meaning. But it helps me a lot. Someone may prefer to call it as the rs232 selector, but I like "expander". Above picture is the sample board, no need to make a pcb.
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