The MAX5481–MAX5484 10-bit (1024-tap) nonvolatile, linear-taper, programmable voltage-dividers and variable resistors perform the function of a mechanical potentiometer, but replace the mechanics with a pinconfigurable 3-wire serial SPI™-compatible interface or up/down digital interface. The MAX5481/MAX5482 are 3-terminal voltage-dividers and the MAX5483/MAX5484 are 2-terminal variable resistors.
The MAX5481–MAX5484 feature an internal, nonvolatile, electrically erasable programmable read-only memory (EEPROM) that stores the wiper position for initialization during power-up. The 3-wire SPI-compatible serial interface allows communication at data rates up to 7MHz. A pin-selectable up/down digital interface is also available.
The MAX5481–MAX5484 are ideal for applications requiring digitally controlled potentiometers. Two end-toend resistance values are available (10kO and 50kO) in a voltage-divider or a variable-resistor configuration.
These devices ideal for applications requiring low-temperature-coefficient voltage-dividers, such as low-drift, programmable gain-amplifiers.
The MAX848xDigitalPotSetWiperPosition and MAX848xDigitalPotDecrement methods ONLY support software SPI.
Methods
MAX848xDigitalPotSetWiperPosition ( word value where range is 0 to 1023 ) Sets the pot value MAX848xCopyWiperRegistertoNVRegister Sets the NVRAM to the current pot value MAX848xCopyNVRegistertoWiperRegister Sets the current pot value to MVRAM MAX848xDigitalPotIncrement Increment the current pot value MAX848xDigitalPotDecrement Decrement the current pot value
What's less "fun" is when it doesn't work, and you can't for the life of you see why. Is it a wiring error? A misunderstanding of the datasheet? Or (and more likely in my case) a silly coding error?
I spent ages yesterday trying to figure out why something wasn't working. I finally spotted that in trying to do something else I'd changed Timer1 to Timer2. As that hadn't worked, I changed everything back to Timer1. Everything that is apart from the code that actually started the timer, it was still starting Timer2. Left with my original problem of why an overflow interrupt triggered every time, when I wasn't expecting it, it took me way too long to realise that my "expected" event should have triggered in 40,000 timer counts. As this then had to wait for another (potential) 40,000 counts before the next event, there was no surprise that the overflow ocurred. No surprise, except to me who'd spent well over four hours on this one problem...
Still, my Grid Frequency Meter is now working and once I've drawn up the circuit I'll post the circuit and code in the Projects and Guides section.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
The MAX5481–MAX5484 10-bit (1024-tap) nonvolatile, linear-taper, programmable voltage-dividers and variable resistors perform the function of a mechanical potentiometer, but replace the mechanics with a pinconfigurable 3-wire serial SPI™-compatible interface or up/down digital interface. The MAX5481/MAX5482 are 3-terminal voltage-dividers and the MAX5483/MAX5484 are 2-terminal variable resistors.
The MAX5481–MAX5484 feature an internal, nonvolatile, electrically erasable programmable read-only memory (EEPROM) that stores the wiper position for initialization during power-up. The 3-wire SPI-compatible serial interface allows communication at data rates up to 7MHz. A pin-selectable up/down digital interface is also available.
The MAX5481–MAX5484 are ideal for applications requiring digitally controlled potentiometers. Two end-toend resistance values are available (10kO and 50kO) in a voltage-divider or a variable-resistor configuration.
These devices ideal for applications requiring low-temperature-coefficient voltage-dividers, such as low-drift, programmable gain-amplifiers.
The MAX848xDigitalPotSetWiperPosition and MAX848xDigitalPotDecrement methods ONLY support software SPI.
Methods
MAX848xDigitalPotSetWiperPosition( word value where range is 0 to 1023 ) Sets the pot valueMAX848xCopyWiperRegistertoNVRegisterSets the NVRAM to the current pot valueMAX848xCopyNVRegistertoWiperRegisterSets the current pot value to MVRAMMAX848xDigitalPotIncrementIncrement the current pot valueMAX848xDigitalPotDecrementDecrement the current pot valueConfiguration
The library is easy to use. Set up the ports, decide on SPI methof (software or hardware), attach the MAX848x and it should work,
Enjoy
Many thanks. I appreciate you sharing this code.
Cheers. It was so easy to do. I took the existing digital pot and improved.
The best part... seeing the pot values come up on my bench meter!!
That's the "fun" part!
What's less "fun" is when it doesn't work, and you can't for the life of you see why. Is it a wiring error? A misunderstanding of the datasheet? Or (and more likely in my case) a silly coding error?
I spent ages yesterday trying to figure out why something wasn't working. I finally spotted that in trying to do something else I'd changed Timer1 to Timer2. As that hadn't worked, I changed everything back to Timer1. Everything that is apart from the code that actually started the timer, it was still starting Timer2. Left with my original problem of why an overflow interrupt triggered every time, when I wasn't expecting it, it took me way too long to realise that my "expected" event should have triggered in 40,000 timer counts. As this then had to wait for another (potential) 40,000 counts before the next event, there was no surprise that the overflow ocurred. No surprise, except to me who'd spent well over four hours on this one problem...
Still, my Grid Frequency Meter is now working and once I've drawn up the circuit I'll post the circuit and code in the Projects and Guides section.