Часы реального времени, в нынешнее время, реализованы в виде отдельной микросхемы, к которой нужно добавить кварцевый резонатор и автономный источник питания. В некоторых микросхемах, кварцевый резонатор встроен внутри. Одни из таких часов на микросхеме DSSN я купил для своих проектов. В примере буду подключать часы реального времени к китайскому аналогу Arduino UNO. Представляют из себя законченный модуль ZS, который можно подключать к различным устройствам, не только к платформе Arduino. Модуль построен на микросхеме DSSN, которая по сути и является часами реального времени.
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Recently, I had ordered several DS boards from my regular eBay vendor in Shenzhen for some testing, only to find two oddities: first, the factory had evidently gotten an incorrect chip with the same sized 0. This chip was the wholly-incompatible DS It happens, particularly at this price point and via gray market suppliers. No worries, I contacted the seller and they sent me a replacement board.
I lifted the pad desoldering the chip that was previously on it, so I had to add the bodge wire to properly connect the SDA pin. The second oddity was that two of the boards I ordered contained a DSM chip, which, though seemingly only a different variant of the same chip, is a somewhat different beast than the DS non-M , in that the non-M variant has a standard Note that although I placed the order for the free sample in August of , the date code on the genuine chip pictured above is from December of Obviously Maxim keeps an inventory of chips in storage, presumably to have a buffer for spikes in demand.
So do the eBay-sourced ones. The laser markings on the packages are nearly indistinguishable, and all the eBay-sourced ones appear to be authentic Maxim chips. After doing some tests with the M variants, two major differences between the two variants became clear. Thus, I felt I should explicitly mention them here.
Here we go: 1. Why is this so? The crystal, which is integrated into the package itself, is connected to the oscillator circuit and array of capacitors which can be switched in and out to steer the frequency. The output of the oscillator is sent to the control system that, after reading the temperature from the temperature sensor, determines the number of capacitors to switch into the circuit to compensate for any changes in temperature. Critically, both of these outputs are temperature compensated.
So depending on the temperature we will adjust the internal capacitive load to maintain a consistent 32kHz frequency across temperature.
However, the DS series is not intended to be used as a 32kHz reference as the design is strictly focused on creating the most accurate 1Hz signal to drive the RTC. Seems reasonable to me: the DS is primarily focused on timekeeping, and the 32 kHz output is a nice bonus. Although the 32 kHz output will be continuous i.
When the temperature conversion and correction happens, there may be a sharp, distinct change in frequency. For systems that require smooth changes in frequency, using a DS as a clock source or frequency standard might not be the best option. For other purposes though, it may work reasonably well. I use mine for driving AVR microcontrollers at low speed, and this works fine.
The resonator signal is sent to both a divider and to the digital adjustment block. If you have a frequency counter or an oscilloscope with a stable reference, you can see the difference between the two chips by probing the 32 kHz output with a proper pullup resistor and then touching the chip with your finger to gently warm it. I have no idea why they designed the chip this way, but it is what it is.
This brings us to the second point. No other frequency options are available. Are you aware of any more? Do you have any idea why Maxim would choose not to have the 32 kHz output of the DSM be temperature compensated?
Why would they not allow for several user-selectable output frequencies and only allow the user to select the 1 Hz output? If you know, please comment!
Major differences between the DS3231 and DS3231M RTC chips
These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Temperature Commercial Frequency Stability vs. Temperature Industrial Frequency Stability vs.
How to Use a Real-Time Clock Module (DS3231)