The boards I received have version "A" of PCF8574. This means that the device address is different. If your code uses 0x20 as the base address, you need to change it. It took me some time to figure that out. EDIT: HiLetgo contacted me after I posted a three star review and offered a partial refund which I accepted. I am updating my rating to four stars based on their customer service and the fact that the boards worked great after I discovered the difference in part numbers and started using the correct address value for version "A" parts. But you should still check your version to see which version you have and refer to the datasheet to find the i2c address associated with that version.
🌐 MCIGICM 2 Channel DC 5V Relay Module: Optocoupler Low Level Trigger Expansion Board for Arduino UNO R3, DSP, ARM, PIC, AVR, STM32, Raspberry Pi
11 Review
REXQualis Comprehensive Starter Kit with Arduino MEGA 2560 & Detailed Tutorial for Arduino IDE Compatibility
11 Review
Gikfun Screw Shield Expansion Board: Enhance Arduino UNO R3 with the EK7007 Add-On
11 Review
🎁 Ultimate BBC Micro bit Sensor Starter Kit: Keyestudio 37-in-1 Box with Tutorial, Compatible with V1.5 & V2, Gift for Kids and Adults (Microbit Board Not Included)
11 Review
M.2 Screw Kit: Easy Mounting for NVMe SSDs on ASUS Motherboards
19 Review
Comprehensive 500pcs Laptop Screw Kit Set for 🔩 IBM HP Dell Lenovo Samsung Sony Toshiba Gateway Acer
12 Review
uxcell 3.5" HDD Screw Black 200pcs for Computer PC Case - Flat Phillips Head - 6#-32 - Hard Drive Fasteners
10 Review
Glarks 660 Pieces Phillips Assortment Motherboard
10 Review