The DATA line is held HIGH (+5V) by a pull-up resistor.
Every seasoned builder has a story about following a schematic exactly and having the interface not work. The reason usually lies in the —the things that are not drawn on the diagram. Here are the most common silent pitfalls: icom ci v usb interface schematic top
Connect from the FT232RL to Pin 8 (VCC) and Pin 7 (Enable) of IC 3 (6N137) . Place a 0.1 F capacitor (C1) between Pin 8 and Pin 5 (GND) of IC 3. Connect RXD from the FT232RL to Pin 6 (Output) of IC 3 . Install a 10 The DATA line is held HIGH (+5V) by a pull-up resistor
The workbench was a graveyard of half-finished projects until the arrived. For a radio op, it wasn’t just a cable; it was the bridge between a legacy rig and modern digital wizardry. Here are the most common silent pitfalls: Connect
Because CI-V is a "half-duplex" single-wire system (the radio and the computer take turns talking on the same wire), you cannot simply tie the TX and RX pins directly together without risk of contention. However, with FTDI chips, there is a trick:
For most users, a PCB based on the offers the best balance of speed, stability, and simplicity.
Building your own Icom CI-V USB interface is a satisfying and educational project. From the elegant simplicity of a two-transistor design to the robust reliability of an opto-isolated FTDI-based interface, you now have the knowledge to choose, design, and build a solution that fits your needs and budget. Understanding the schematic—the "top view" of the circuit—empowers you not just to assemble components but to be a true troubleshooter and innovator in your own ham shack.