Tag Archives: TTL

Three Ways to Make Arduino Works As A USB/TTL Converter

Even if you have years working with electronics, you will still find some simple hacks that you never thought about before. Personally and to save money, when I was a student with a very limited budget I knew that my Arduino UNO can work as a USB/TTL(serial) converter. I used to remove the Atmega328P from my Arduino UNO R3 board in order to use the board as a converter not as a development board.

Why we need to do some tweaking to Arduino in order to use 0 and 1 pins for direct USB <-> UART conversion? This is because of what’s called fan-out (fan-out of a logic gate output is the number of gate inputs it can drive). In Arduino UNO case, the RX & TX lines (pins 0 and 1) are connected to FT232RL/Atmega8U2 USB to TTL bridge and to the Atmega328P MCU (check the schematic). So using the same pins with an external connections without doing any changes to Arduino UNO board probably won’t work.

Patel Darshil over Hackster.io listed three ways to make Arduino works as a USB/TTL converter:

Hack #1: Set Pin 0&1 Mode to Input Mode

This is done using code:

Pin Mode Set Arduino

But why this solves the problem? Well, GPIO can operate in two modes, input and output. In the input mode the equivalent impedance of the pin is too high; therefore, the Arduino/Atmega328P’s pins will have almost no electrical effect to the converter RX/TX pins.

Hack #2: Keep Atmega in Reset Mode

Just connect the RES pin with GND (the bold red wire in the image bellow)

Arduino Reset
Image Courtesy of Patel Darshil

GPIOs are configured using special registers. For example, Atmega has GPIO port data direction register (DDR) to set the GPIO as an input or an output for each port. The value of this register is cleared during reset. Therefore, the MCU’s GPIOs mode will be input. This means high impedance, subsequently.

Hack #3: Remove The MCU

This is the common way used by most Arduino UNO users, but it’s not applicable when it comes to new versions of Arduino; where, the MCU is SMD and can’t be removed.

LED Based Strobe For Entertainment, Events & Warning Signals

Strobe provides regular flashes of light. Usually Strobes are designed using Xenon Tubes. Here is LED based simple solution that can be used as strobe for entertainment and events and also as warning signals. Project is based on PIC16F1825 micro-controller with two digit frequency display.

Project provides TTL output signal, frequency 1Hz-25Hz, Tact switches provided to set the frequency.

This project works along with DC Output Solid State Relay

Features

  • Supply 4.5 to 5V DC
  • Frequency 1Hz To 25Hz
  • Easy Interface with Relay Board
  • Easy Interface with Solid State Relay
  • On Board Power LED
  • On Board Output LED
  • Onboard Switch to set the frequency
  • 2X7 Segment 0.5 Inch Display

LED Based Strobe For Entertainment, Events & Warning Signals – [Link]

Inside the 74181 ALU chip: die photos and reverse engineering

A detailed die photos and reverse engineering of the 74181 ALU chip by Ken Shirriff:

What’s inside a TTL chip? To find out, I opened up a 74181 ALU chip, took high-resolution die photos, and reverse-engineered the chip.1 Inside I found several types of gates, implemented with interesting circuitry and unusual transistors. The 74181 was a popular chip in the 1970s used to perform calculations in the arithmetic-logic unit (ALU) of minicomputers. It is a moderately complex chip containing about 67 gates and 170 transistors3, implemented using fast and popular TTL (transistor-transistor logic) circuitry.

Inside the 74181 ALU chip: die photos and reverse engineering – [Link]

8 Channel Optically Isolated IO Board

8-channel-optically-isolated-io-board-c047_w

Opto-Isolated I/O Board offers a compact & convenient way to interface industrial type inputs/outputs to your microcontroller boards, Signal transmission between circuits of different potentials and impedances etc.

Specifications

  • 4 opto-isolated inputs & 4 opto-isolated outputs
  • Std TTL input signals for opto-couplers
  • Interfacing is via 10-pin Box Header and Screw terminal type connector
  • Power source LED indicator
  • Four mounting holes 3.2 mm each
  • PCB dimensions 54 mm x 64 mm

8 Channel Optically Isolated IO Board – [Link]

RELATED POSTS

DIY USB to TTL Converter

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ams31 @ instructables.com show us how to build a DIY USB to TTL Converter using CH340G IC.

Lots of USB to TTL modules are available in the market based on various chips like PL2303, FT232, CP2102 and CH340g. I have decided to use CH340g IC. Low costing clones of Arduino UNO & Arduino Nano also uses CH340g IC. And this IC is now easily available in India. Reasons for not using other converter IC’s.

DIY USB to TTL Converter – [Link]

16 Channel InfraRed remote controller

16-Channel-Infra-Red-remote-controller-001

16 Channel Infra-Red remote controller is based on PIC16F73 Microcontroller from Microchip. The receiver part follows RC5 (Philips) Code Format. Tiny receiver provides 16 latch outputs or 8 Latch + 8 Momentary outputs by closing Jumper J1. All outputs are TTL and can drive Relay board or solid state relay. The circuit uses TSOP1738 Infra-Red receiver module which provides high degree of noise immunity against interfering light source.

Features

  • Supply Remote Transmitter RC5 Philips 2XAAA Battery
  • Supply Receiver 7V to 12V DC
  • Modulation 38Khz
  • Philips RC5 Code Format
  • Operating range up to 20 feet
  • 2 Pin Screw Terminals for Supply Input
  • On Board Power LED
  • Onboard VT (Valid Transmission) LED
  • All Outputs TTL Level provided with Header Connector
  • Jumper (J1) for Mode Selection
  • J1 Open 16 Latch Outputs
  • J1 Closed 8Latch + 8 Momentary

16 Channel InfraRed remote controller – [Link]

Butchered USB TTL Serial Adaptor

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Aaron Brady writes:

We popped open the case, and there were two main ICs, a Prolific 2303 (the USB to Serial IC) and a ADM3251E (the RS232 line level convertor). I tried to desolder this with no success, but Bas stepped in, cut the leads with a craft knife and ran the iron over the chip’s leads and it basically fell off. He also did the very fine soldering to pins 1 and 5 of the Prolific chip, TX and RX respectively.

Butchered USB TTL Serial Adaptor – [Link]

Dual DC Motor Driver For Robot with L298

L298-DUAL-DC-MOTOR-MODULE-M080AA-500x500

Dual Motor L298 H-Bridge Control project can control two DC motors connected to it. The circuit is designed around popular dual H-Bridge L298 from ST. This board can be configured to drive a single motor with high current rating also. This can be achieved with the help of jumpers on the board. An onboard 5V regulator can take a maximum of 18V of DC input. Should you wish to drive this board with higher voltage then 18V, you will need to connect a external 5V regulated source to the logic circuit. For this you will need to remove J-5V. This board can fit in any small toy or robot due to small size and very low profile. L298 IC is mounted under the PCB in horizontal position to make board small and low profile to fit any small robot. On board 5V regulator can be used to power up external Micro-Controller board as well as internal logic supply.

Features 

  • Motor supply: 7 to 46 VDC
  • Open J-5V Jumper if Input Motor Supply is above 18V ( Required External 5V for Logic)
  • Control Logic Input: Standard TTL logic level
  • Output DC drive to motor: up to 2 A each (Peak)
  • On Board 5V Regulator (Close J-5V to Use On Board 5V Regulator)
  • Enable and direction control pins available
  • External Diode Bridge for protection
  • Heat-sink for IC

Dual DC Motor Driver For Robot with L298 – [Link]

AC Solid state Relay for Inductive Load

 

M015_W

AC Solid state Relay for Inductive Load offers simple On/Off type Switch Control with TTL compatible input signal.

  • Input signal : 2 ~ 5 VDC, TTL compatible
  • Output : up to 500 W
  • Mains supply input 230 VAC or 110 VAC
  • Optically isolated Triac based design
  • Power Battery Terminal (PBT) and Terminal pins for easy input / output connection
  • Four mounting holes of 3.2 mm each
  • PCB dimensions 35 mm x 72 mm

AC Solid state Relay for Inductive Load – [Link]

RELATED POSTS

5V & 12V Regulated Power Supply

Regulated_PSU_G035_1

This project can be used to power up TTL and CMOS based projects, it provides 5 VDC & 12 VDC outputs with an onboard mains transformer.  The project is based on the industry popular 7800 series voltage regulator in TO220 packages.

Features

  • Input: 240 VAC
  • Output: 5 V, 12 V @ 600 mA regulated low ripple DC voltage
  • Thermal overload/short circuit protection (provided by IC feature)
  • Power Battery Terminal (PBT) for easy input and output connection
  • External On/Off switch connection possible
  • LED indication for outputs
  • Four mounting holes of 3.2 mm each
  • PCB dimensions 87 mm x 49 mm

5V & 12V Regulated Power Supply – [Link]