Are there any UART to GPIO bridge chips? - Page 1
Forum section: electronics / beginners

author: LinuxHata
author_rank: Frequent Contributor
timestamp: August 09, 2023, 06:47:47 pm
content: Hello.I'm in search of a chip, which will accept signal via UART (TTL), 9600bps at least, and will have either 8 or 16 (preferrable) parallel outputs (no need for inputs).There are the following solutions, which I don't like:74HC595 - Requires 3 wiresPCF8575 and other I2C expanders - require 2 wires.DS2408 - Mega pricey!TCA5405 - few outputs, hard to solder ICI went into communist side of the chip making and found TM1652 - This IC accepts UART at input, and can drive up to 42 LEDs. But the issue is, that this is a dedicated LED driver IC, which does multiplexing, so unusable for general on/off outputs.Any ideas?

author: langwadt
author_rank: Super Contributor
timestamp: August 09, 2023, 07:14:51 pm
content: what ever cheap MCU with enough pins you fancy

author: gnuarm
author_rank: Super Contributor
timestamp: August 09, 2023, 07:25:31 pm
content: A small MCU is typically easy to program. Develop your own protocol and write programs for both the controller device and the slave MCU.If that doesn't work for you, a small FPGA is not hard to design.I don't know if you can find a one-wire chip to do what you want, but if you can, you can rig up a simple open collector interface to talk to it through a UART. Since they are addressable, you can use several of them on the same interface. You can set the bit rate timings to match the one-wire timing easily. One UART character maps to a single one-wire bit.DS2408https://www.analog.com/en/products/ds2408.html#product-overviewhttps://www.analog.com/en/app-notes/reading-and-writing-1wirereg-devices-through-serial-interfaces.html

author: LinuxHata
author_rank: Frequent Contributor
timestamp: August 09, 2023, 07:43:32 pm
content: I'm looking for "plug and play" solution, not DIY, as in case with MCU.

author: gnuarm
author_rank: Super Contributor
timestamp: August 09, 2023, 07:53:15 pm
content: Quote from: LinuxHata on August 09, 2023, 07:43:32 pmYou have to write code for the controller no matter what. Using the one-wire chips only require a single transistor and a pullup resistor. Maybe something to protect the UART input like a diode to 3.3V.What will be driving this?

author: Benta
author_rank: Super Contributor
timestamp: August 09, 2023, 08:07:23 pm
content: The classic chip for doing this is the 16550.https://en.wikipedia.org/wiki/16550_UARTAlso available as dual and quad parts. Super simple to use.

author: edavid
author_rank: Super Contributor
timestamp: August 09, 2023, 08:18:44 pm
content: Quote from: Benta on August 09, 2023, 08:07:23 pmI think you are confusing it with some other part, since the 16550 is register programmed.Perhaps the IM6402/HD6402? That is fine if you don't mind using surplus parts.https://www.jameco.com/z/CDP6402CE-INTERSIL-CORPORATION-IC-6402-CMOS-UART-DIP-40-pin_43158.htmlOP, the 74LV8153 is still in production, but costs more than an MCU:https://www.findchips.com/search/74lv8153

author: DavidAlfa
author_rank: Super Contributor
timestamp: August 09, 2023, 10:35:17 pm
content: +1 the cheapest MCU will be the best option, uart shift registers are a very rare thing.The required program is extremely simple while you could implement all Sort of features like setting Hi-Z, open drain, even input and serial half-duplex mode using only one wire.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 09, 2023, 10:44:11 pm
content: You can try to get an 16550 or an Z80-SIO.Back in those days every microcontroller family had it's own solution for connecting a serial device to an 8-bit parallel bus.Some were locked in to the bus used by a certain controller, others were adaptable to a few different microprocessors.

author: LinuxHata
author_rank: Frequent Contributor
timestamp: August 10, 2023, 03:54:04 am
content: These chips have to be used in class, so if I select MCU, it means that I should write a code, then get chips, program them, make tests, etc. Why should I bother, if there's a ready made solution available?I checked the chinese suppliers, and knock off SN74LV8153 is available for around 50 cents, so here we go, and thanks for suggesting it!

author: amyk
author_rank: Super Contributor
timestamp: August 10, 2023, 04:11:13 am
content: It'll be much cheaper to use an MCU, and the learning curve seriously isn't that hard.Check whether the data format of the '8153 fits your needs.

author: LinuxHata
author_rank: Frequent Contributor
timestamp: August 10, 2023, 04:16:37 am
content: Please read above

author: DavidAlfa
author_rank: Super Contributor
timestamp: August 10, 2023, 04:24:12 am
content: If you really get them for that price, great!I tried searching and it seemed to be a really rare and exotic chip.I even found threads from 2005 asking the same thing and they were already unobtanium.If it's for class, then they might already have some MCUs available like PIC, STM32, AVR... , ask them, we will make that program in no time!

author: LinuxHata
author_rank: Frequent Contributor
timestamp: August 10, 2023, 10:24:40 am
content: Theoretically, I can write MCU software by myself, but ready made, "hardware" solution is far better.I ordered 50 pcs. of these chips, will have them on hands in 2 weeks or so, and will let you know how they perform.

author: edavid
author_rank: Super Contributor
timestamp: August 10, 2023, 01:45:02 pm
content: Quote from: DavidAlfa on August 10, 2023, 04:24:12 amHow can it be rare and unobtainium when DigiKey and Mouser have thousands in stock?Now if you said it was overpriced, I would agree.It will be really interesting to see if the 50 cent chips are functional.

author: DavidAlfa
author_rank: Super Contributor
timestamp: August 10, 2023, 01:56:30 pm
content: You're right, I saw them at $4 each lol.But nothing in AliExpress!

author: LinuxHata
author_rank: Frequent Contributor
timestamp: August 10, 2023, 07:55:43 pm
content: Well, in most cases, these knock-off chips do work, but with certain limitations.For example, fake DS3231 might have VDD directly tied to VBAT, so if you connect external battery, you will get bada-boom...Also, fake DS3231 do not like to be polled too quickly - they start loosing time, several minutes per hour...Fake LT1249 has UVLO at 10V, instead of 12V and so on

author: LinuxHata
author_rank: Frequent Contributor
timestamp: September 09, 2023, 09:34:19 am
content: Well, they arrived, have not tested yet, but they look like legit TI chips....

author: Messtechniker
author_rank: Frequent Contributor
timestamp: September 09, 2023, 02:25:38 pm
content: Will something like this fit your bill?https://www.electronic-software-shop.com/lng/en/hardware/digital-io/?language=en