Top [work] — Icom Ci V Usb Interface Schematic

Connect a between the TXD line and the RXD line. The cathode (the side with the stripe) must face the TXD pin of the serial chip.

Purpose: This allows the TX pin to pull the bus low but prevents it from forcing the bus high, maintaining the open-collector requirement.

This small detail is exactly where the phrase becomes useful: the top‑level view of a system may show just a rectangle labeled "CI‑V bus driver", while the detailed schematic reveals the 7417 or a discrete transistor configuration that actually implements that driver.

Once construction is finished, it is time to test the interface.

Set both DTR and RTS to "Low" or "None". icom ci v usb interface schematic top

A direct connection uses a simple USB-to-TTL serial adapter directly connected to the radio. While cheap, this creates a direct electrical path between your computer’s switching power supply and your sensitive HF transceiver. This often introduces significant USB ground loop noise (RFI) into your receiver and risks damaging equipment if a voltage differential occurs.

A reliable USB-to-CI-V interface requires components that balance driver stability, noise immunity, and ease of assembly. USB-to-Serial Bridge The heart of the interface is the USB-to-UART bridge IC.

Implement two entirely separate ground copper pours. Label one GND_USB and the other GND_RADIO . Never connect them together on the board.

Because the USB bridge separates data into distinct TXD and RXD pins, you must combine them into the single-wire CI-V line without causing data collisions or looping your own transmissions back into the computer blindly (though the CI-V protocol natively expects to "echo" transmissions back to the controller). Optoisolation (Highly Recommended) Connect a between the TXD line and the RXD line

If you prefer not to build, several commercial products are regarded as top-tier: Icom CT-17

If you suffer from electromagnetic interference (EMI) or want to completely eliminate ground loops between your computer and your rig, an isolated schematic utilizing optocouplers is the gold standard. The Schematic Circuit:

Connect all PC-side grounds together: FT232RL GND, Pin 5 of IC 2, and Pin 5 of IC 3. Step B: Wiring the Radio Side (Isolated Domain)

Snap a small onto the cable near the radio connector. Construction and Testing Steps Step 1: Assembly This small detail is exactly where the phrase

The Icom CI-V USB interface is – it is a bidirectional, inverted, open-collector level converter. The top schematic presented here (USB serial chip → NPN inverter/open-collector → CI-V bus with pull-up) has become a de facto standard because:

If you are searching for "icom ci v usb interface schematic top", you are probably looking for a clear diagram of a that includes the correct bus driver, not just a UART‑to‑CI‑V connection sketch. The G3VGR design—or a modern variation using a CP210x board with an external 7417—is an excellent starting point.

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:

When the USB chip transmits a logic high (5V), the diode blocks it, and the pull-up resistor keeps the CI-V bus high. When the USB chip transmits a logic low (0V), the diode conducts, pulling the CI-V bus down to ground. When the radio transmits, it pulls the line low, which travels directly into the RX pin of the USB chip. 4. PCB Layout and "Top" Silk Architecture