# SchemaHD — Generate Verilog & Simulation.

> Logic circuit schematic design, Verilog HDL generation, and simulation tool for FPGAs. (iPhone/iPad app by Yasuaki Iwasaki.)

- Source: https://appshunter.io/ios/app/schemahd/id1578851758 (this page in markdown: same URL + `.md`)
- Developer: [Yasuaki Iwasaki](https://appshunter.io/developer/560857505)
- Category: Developer Tools, Productivity
- Price: Free with in-app purchases
- Rating: 3.00/5 from 2 App Store ratings · 2 written reviews indexed
- Age rating: 4+
- Requires: iOS 14.0 · 2 MB
- Languages: English, Japanese
- Released: 2021-08-10
- Data updated: 2026-06-06
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/schemahd/id1578851758/reviews.md

## What is SchemaHD?

FPGAs can dynamically generate logic circuits by means of configuration bit streams generated by languages such as Verilog and VHDL.
The generated logic circuit cannot be changed by communication data.
Therefore, it is very safe and cannot be attacked by hacking, which is a problem with CPUs, to execute arbitrary commands.
In addition, the generated logic circuits are all running simultaneously, so the highest performance parallel processing is being performed.
It can also generate logic circuits using configuration bitstreams at very high speed.
Most of the processing that can be done by the CPU can be done by the FPGA alone.
With advanced security and the highest performace, FPGAs are the perfect device for the modern age.
However, it takes a lot of effort to learn languages such as Verilog and VHDL.
There are other methods such as high-level synthesis from C/C++, but they require a lot of adjustments such as #pragma, and do not maximize the capabilities of the FPGA.
Schematics, not programming languages, are needed to maximize the capabilities of FPGAs and to further improve developer productivity.
Schematics allow you to grasp the whole picture at a glance, and can perfectly represent parallel processing.

SchemaHD is to draw a circuit diagram of a logic circuit, and it's possible to do generation of Verilog HDL and a simulation.
A made circuit diagram can be used by a different circuit diagram immediately.
You can also install wiring easily by touch operation.
A concept of interface is adopted as a terminal, so something structured of a AXI bus can also be used.
A terminal it's also possible to distinguish sound argument reason, negative logic and characteristic wiring of a clock and a reset by interface, and which is different in interface, they don't seem able to connect, it is.
You can input and output as a JSON file, so the made circuit diagram and interface are also capable of cooperation with other application.
Verilog HDL generated from a circuit diagram contains a comment of a terminal name and an instance name, so it's capable of the correspondence which is at the time of problem occurrence.
A network connection isn't needed, so it's also effective in information leak prevention.
A simple simulation is offered in the present, but it's expected to enhance it early.

## Key features

- Draw logic circuit diagrams
- Generate Verilog HDL
- Perform circuit simulations
- Touch-based wiring
- AXI bus interface support
- JSON import/export
- Offline network operation

## Pricing and in-app purchases

Base price: Free.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Give a tip #1 | $1.99 | one-time |
| Give a tip #2 | $3.99 | one-time |
| Give a tip #4 | $15.99 | one-time |
| Give a tip #3 | $7.99 | one-time |
| Give a tip #5 | $23.99 | one-time |
| Give a tip #6 | $39.99 | one-time |
| Give a tip #7 | $79.99 | one-time |


## Recent user reviews (2 of 2)

All indexed reviews: https://appshunter.io/ios/app/schemahd/id1578851758/reviews.md

### 1/5 — Unintelligble

*2023-05-05, version 1.2.2*

Cool concept, but unable to use as the directions are intelligible and there are no examples.  It appears the ‘help file” was translated via computer.  Unable to figure out how to create and simulate file or to export verilog.  UI needs work. 
Has potential to be useful if author provided genuine English translation with tutorial and sample templates. I would love to try an updated version that addresses my concerns.

### 5/5 — Export Verilog file seems not working

*2022-04-14, version 1.2.2*

Very interesting app. I’m trying to understand how it works, but it seems that clicking the export Verilog buttons doesn’t do anything.

## Frequently asked questions about SchemaHD

### What is SchemaHD used for?

SchemaHD is used to draw circuit diagrams for logic circuits, generate Verilog HDL code, and perform simulations. It aims to simplify FPGA development by using schematics.

### Does SchemaHD support offline use?

Yes, SchemaHD does not require a network connection, making it effective for information leak prevention and usable in offline environments.

### What programming languages does SchemaHD replace?

SchemaHD replaces the need to learn complex programming languages like Verilog and VHDL for FPGA development. It offers a schematic-based approach.

### Can I import and export my circuit designs with SchemaHD?

Yes, you can input and output your circuit diagrams and interfaces as JSON files, allowing for cooperation with other applications.

### What is the rating of SchemaHD?

SchemaHD has a rating of 3.0 stars based on 2 user ratings.

### Is SchemaHD available on multiple devices?

Currently, SchemaHD is supported on iPads.

### How often is SchemaHD updated?

The latest version, 1.2.4, was last updated on September 18, 2024. Updates are released periodically to enhance features like simulation capabilities.

### What is the age rating for SchemaHD?

SchemaHD has an age rating of 4+, making it suitable for a wide range of users.

## Version history (last 5 releases)

### 1.2.4 — 2024-09-18

Corrected a problem that causes the application to close abnormally when operating the tool selection in the upper right corner of the drawing edit screen.

### 1.2.3 — 2024-09-17

Fixed a problem that prevented Verilog export.

### 1.2.2 — 2022-03-16

Bug Fix: The wheel shape of the picker, such as part selection, and the area to be tapped are now different.

### 1.2.1 — 2021-10-07

Bug fix: Fixed an issue where picker shapes such as part selection were displayed in a different format from the wheel format on iOS 15.

### 1.2.0 — 2021-09-27

New feature: PDF output of schematics is now available. This can be done from the design screen of the drawing.
Bug fix: The icon for Logic and Bipolar part selection is not displayed.

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-06.*