Description: The smallest and easiest to use serial conversion circuit on the market! This board has one purpose in life - to convert RS232 to TTL and vice versa (TX and RX). This will allow a microcontroller to communicate with a computer. Shifter SMD is powered from the target application and can run at any voltage! That’s right - power the board at 5V and the unit will convert RS232 to 5V TTL. Power the board at 2.8V and the Shifter board will convert RS232 to 2.8V CMOS TTL. Includes two indicator LEDs for TX and RX. Runs from 300bps up to 115200bps.
This version comes with no DB9 connector attached. Useful for field installations and projects where RS232 serial is coming from something other than a DB9 cable.
Based on 6 ratings:
2 of 2 found this helpful:
I could receive using this board (after realizing I needed a null modem), but couldn’t send signals properly. I ended up getting a MAX232 which is working perfectly – should have gone that route all along for my project.
1 of 1 found this helpful:
I was powering this with VCC=5v and wondering why the TX-O wasn’t producing a signal on the RS232 side.. while my MCU can accept 5V signals, it only produces 3.3v logic level outputs.
Switched the VCC to 3v3 and everything is working perfectly!
I have this device installed in a Motorola Micom Mobat 2ET radio, along with the Bluetooth Mate Silver WRL-12576, and the wireless serial connection is fantastic. Bidirectional data transfer is fully functional.
What may not be clear to someone who cannot read a schematic, and understand the circuit, is that the TX-0 on this board connects to the RXD on the serial device while the RX-1 on this board connects to the TXD on the serial device. When properly connected, this functions perfectly.
I’m hooking this up to a RPi3 in order to communicate with an RS232 device. On the RPi, I connected the 3.3V to Vcc, GND, UART0 TXD to TX-0 and UART0 RXD to RX-1. When sending from the RPi, the TX LED blinks, but the signal coming out on the DB9 RXD pin is only the leading edge of each bit and is only about 100mV in amplitude.
I tried to connect the DB9 RXD to TXD and read off the RX-I pin, but nothing comes across. Sadly, it appears this device does not work as advertised.
You can reach out to our technical support department here: https://www.sparkfun.com/technical_assistance I am sure they would be happy to assist you to the best of their abilities.
I’m using one of the bi-directional logic converters (BOB-12009) - the lights come on for both RX & TX but no signal on the RS232 transmit when my processor sends a signal. All I can figure is the logic converter doesn’t have enough power. I spent about $50 on 5 of ‘em - can’t get any to work. Used brand new converter and separate new power supply. Must be a bad batch.
For more information about RS232 and TTL serial, try looking at our tutorial here => [ https://www.sparkfun.com/tutorials/215 ].
We tried converting RS232 voltage down to 1.8V but it was not able to work. The lowest seemed to be around 2.1V with the RS232 Shifter. We recommend using the RS232 Shifter running at 5V (or anything higher than 2.8V) for the TTL side and further convert the signal down to 1.8V with the TXB0104 [ https://www.sparkfun.com/products/11771 ]. The TXB0104 can translate down to 1.2V. Make sure that you have 5V and 1.8V to set the logic levels with each respective TTL side.