Expand your GPIO! PCF8574 & MCP23008 скачать в хорошем качестве

Expand your GPIO! PCF8574 & MCP23008

High quality PCB Services https://pcbway.com Welcome to another Voltlog, in this video we're going to take a look at an easy way of adding more GPIOs to your project because if you’ve been tinkering with electronics at some point sooner or later you’re going to need more GPIOS than what’s available from your microcontroller. →Checkout my Tindie store https://voltlog.com/y/tindie →PCF8574 Datasheet https://voltlog.com/y/489mb →MCP23008 Datasheet https://voltlog.com/y/v7rbx →Evaluation Board Source [Github] https://voltlog.com/y/lumxj →ESP32 Tasmota Valve Controller [Tindie] https://voltlog.com/y/s7rc4 →Support the channel via Patreon, Paypal or Bitcoin http://www.voltlog.com/donations →Support the channel by clicking these links (CommissionsEarned) Aliexpress http://voltlog.com/y/kr0sa Ebay http://voltlog.com/y/jzkfp Amazon.com http://voltlog.com/y/qw4d3 Banggood.com http://voltlog.com/y/o4025 →Blog Post http://www.voltlog.com/ #PCF8574 #MCP23008 #GPIO Luckily this problem is not new, it has been around since the introduction of digital processors so there is a very convenient solution to our problem in the form of GPIO expanders. They can come in many shapes and sizes but the key feature is that they usually take a serial input which means a low pin count for the input and they provide a number of different outputs depending on the package. So here is for example the datasheet for a very popular GPIO expander chip, this is the PCF8574, the datasheet is from NXP but this is manufactured by different companies and this is a big plus because there is a higher chance of finding these in stock. If we take a look at the block diagram we notice, there is an I2C interface, there are 3 pins for settings the address on the I2C bus, this way we could have up to 8 of these chips on the same I2C bus each with its own address, there are 8 GPIOS at our disposal and we have some bonus features like the interrupt pin which could signal to our controller when there is a state change so we don’t have to keep polling the chip, because this chip provides input and output capability. So by using just 2 pins for the I2C bus, we get 8 GPIOs in return, which is pretty neat. This particular device can drive up to 10mA per port with a max total of 80mA per package, but you can also parallel output ports together to drive more current to a single load if that is needed. So it’s pretty comparable to what you would get with a typical microcontroller. There are also variants of this chip that have a higher current drive capability up to 200mA per package and they repurpose the INT pin as an address pin which expands the total number of devices on a single bus up to 64. So you will certainly find something that suits your needs. Another popular option is the MCP23008, this has similar functionality I2C or SPI input interface, 8 GPIOs, 3 address pins so up to 8 devices on the same bus, interrupt capability, up to 125mA total per package with up to 25mA per pin. Fairly similar specs and I could be using any one of these chips for my application, the decision will probably come down to cost and availability for the particular package that I will end up using. With these two options in mind, I went ahead and designed an evaluation board in Kicad, because first of all I would like to evaluate how the firmware support is like for these chips and I also would like to confirm that there is no unexpected behavior because I will be using these to drive triacs that control some mains powered load, I want to make sure everything works as expected.