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My prototype was going to use 74HC589 as a parallel to SPI interface for ESP8266-07 MCU. They are in short supply for quick delivery at the moment.

I am asking for suggestions for a similar chip that is suitable to replace it on a 3.3v supply, with a tri-state output, that I might be able to procure more quickly. It is a new design that is being prototyped on wire-wrap and strip-board, so it does not have to be pin compatible. A SOP package is OK, but a DIL/DIP is preferable though.

It is to be used as a 8 bit parallel to SPI input on a bus that has multiple chip select inputs, which is why it needs a tri-state output. It will be taking inputs from several RA-02 LoRa modules.

I have the 74HC165 in stock, but unless I am reading the data sheet wrong, that does not appear to be tri-state.

This is my first question here, so apologies in advance if I have overlooked the obvious. My favourite search engine has not yet turned anything suitable up.

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  • \$\begingroup\$ Have you considered using a standard SPI port expander, such as the MCP23S17? It's a little more complicated to drive, but a lot more general-purpose. \$\endgroup\$
    – Dave Tweed
    Mar 16, 2019 at 22:33
  • \$\begingroup\$ Thank you @DaveTweed, that looks like a very good suggestion. It is a little pricey by comparison. It is to be a low cost open source project when it's working, so I want to keep it to cheap readily available parts that can be found easily on well known auction sites and local parts stockists, \$\endgroup\$
    – birdwes
    Mar 16, 2019 at 22:38
  • \$\begingroup\$ Do you need the full \$30\:\text{MHz}\$ capability of that device? Or, what's the rate you need? Also, you mention the 74HC165. Can you just add a tri-stating buffer to its outputs? \$\endgroup\$
    – jonk
    Mar 16, 2019 at 22:42
  • \$\begingroup\$ @jonk, LoRa on transmits at a maximum rate of much less than 64kb/s, so speed is not an issue. It's not a battery power device, so I can afford enough power to poll the inputs and don't need a "pin change interrupt". The only other things that share the SPI bus are a LCD display (128px * 160px) and a 74HC595 for status display LEDs. \$\endgroup\$
    – birdwes
    Mar 16, 2019 at 22:50
  • \$\begingroup\$ @birdwes GIven that you are running into stock issues and cost is an issue, I'd consider some Microchip (they never kill an IC, it seems, unlike many other companies) MCU for this. The data rate is slow enough that the coding should be easy. Costs for the right number of pins might be competitive with your HC589, too. What did you pay for your HC589's? And are you able to consider yet another programming toolchain, anyway? Also, a discrete tri-state output isn't hard to add to an existing output for an IC you can get. \$\endgroup\$
    – jonk
    Mar 16, 2019 at 22:59

1 Answer 1

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Have you considered using a standard SPI port expander, such as the MCP23S17? It's a little more complicated to drive, but a lot more general-purpose.

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  • \$\begingroup\$ thank you. I did not know about this component until I asked this question. The version 1 prototypes are going ahead with the hardware I was asking about, but I shall definitely try these in the version 2. \$\endgroup\$
    – birdwes
    Mar 28, 2019 at 1:03

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