PCB PMOD Request: Unique I/O expander

[chili-chips-ba]

While working with Olimex GateMateA1-EVB, we realized that there was only one push-button at user disposal, whereas our TetriSaraj game needed five. Similarly the number of user LEDs is inadequate for debugging (@TsvetanUsunov, take note).

We believe that many other examples would also benefit from a richer complement of LEDs and buttons, and recommend providing a PMOD with an 8-bit bank of each.

Given that this problem is due to GateMate somewhat lower I/O count compared to FPGAs in the same category (@DadoCCAG, take note), these 16 additional lines should come from a GPIO expander based on 1-Wire protocol, and would therefore consume only one FPGA I/O pin for the gain of 16 (or more) slow user I/Os.

To enable this new PMOD hardware, we shall within this project develop RTL for 1-Wire Controller.

[chili-chips-ba]

@goran-mahovlic, the 1-Wire Controller Example is now available:

• https://github.com/chili-chips-ba/openCologne/tree/main/2.Simple--4--1Wire-Controller

[goran-mahovlic]

Do you maybe have some chip on your mind that we could use? I have only used I2C ones with IRQ capabilities.

[chili-chips-ba]

• TCA5405 is an interesting and minimalistic device (5 channel)
• DS2408 has 8 channels and is more expensive

There are also Real-Time Clock devices with 1-wire interface such as DS2417.

We are certain that the Far-Eastern silicon suppliers have their own equivalents at lower price points. If that option is open, we can also list some from their portfolio.

[goran-mahovlic]

DS2408 is really overpriced - on Mouser it is more then 10€

We are certain that the Far-Eastern silicon suppliers have their own equivalents as a lower price points. If that option is open, we can also list some from their portfolio.

Sure! I am just preparing orders from LCSC so if something is available there it would be perfect!

[chili-chips-ba]

As 1-Wire GPIO expanders seem rather scarce, we could amend the plan and build an I/O expander that's truly different from the rest of the crowd. Here are some options:

---1--- Differentiate by capacity, such as by offering a large number of I/O

• PCA9505 - 40 GPIO 400kHz I2C, with integrated 100K pullups

---2--- Differentiate by extra functionality, such as by offering GPIO with built-in FIFOs, UARTs, PWM, Keypad, PowerWakeup, etc.

• SCH3221 - 33 GPIO, Quad 460kbps UARTs, Dual 4Mbps IrDA, Watchdog, Wakeup, PWM
• LM8330 - 20 GPIO with Keypad/PWM controller and power Wakeup
• STMPE1601 - 16 GPIO with Keypad/PWM controller and power Wakeup

• ADP5586 - 10 GPIO with event FIFOs and PWM

  ---3--- Differentiate by speed, such as by offering 26MHz SPI instead of 400kHz I2C, possibly also with integrated Level Shifters

• MAX7301 - 28 GPIO via 26MHz SPI

  • MAX7317 - 10 GPIO via 26MHz SPI, with oversized 7V/24mA open-drain outputs

  • XRA1405 - 16 GPIO via 26MHz SPI with Level Shifters

• XRA1404 - 8 GPIO via 26MHz SPI with LS

• XRA1403 - 16 GPIO via 26MHz SPI, without LS

  ---

  The SCH3221 option is very interesting and most challenging.

[goran-mahovlic]

Would it be ok if we start with something simple like PCA9535

I have that one at home as we have used it in MegaPhone project...

We could use it with few LEDs and Keypad Matrice as a PoC - then if needed per project we could add any of the complex ones?

PCA9505 is also fine but I will need to order it, and we need to check what would it be connected to...

I also do not know if it is better for you that we use PMOD form factor for this one or we could use one of Olimex top 3 connectors?

[chili-chips-ba]

PCA9535 is very popular and also available on LCSC. It does the job, but it does not add the uniqueness.

For the latter, we are proposing to add a ULN2003 into the mix. That would also justify the use of top Olimex connector, which has more pins than a PMOD -- We would now not be blocking them without adding value.