micro SD Adapter – is an ease and only this type construction on Polish market. It is definitely different from other similar competitive products because of a key functionality related to power control possibility from microcontroller level. Thanks to it we can build even more reliable constructions especially because no other memory card won’t “hang up” never again during work. But even if, then from the microcontroller level we can reset it by switch the power on and off. Operation of this functionality is present even in ready and well known to wide audience of programmers - libraries Fat FS and thanks to our book: "C language Passion of 8-bit controllers programming" – also in Petit FS libraries. In the book there are many practical examples described with the use of memory cards with particular attention to the functionality described above.
We set new trends on the national market of educational modules. Just like we did in case of using for the first time in Poland the converters to power the ATB start-up kits in situation when after few month of their existing on the market, our competition woke up and started to use similar solutions. Now a new module of a memory card show up on the market. Maybe for some time some other companies will follow our steps and add this described functionality to improve quality of own products. Our approach clearly confirms the fact that we do not follow fashion. Our evaluation kits and modules such as the adapter are produced not only for education purposes. Another thing that differ our module from competitive ones is not only miniaturization and high quality made products but also high quality power filtration what is often forgotten by other manufacturers but also construction of the module that provides possibility to use it in own designs. From the bottom of the module there is goldpin-type connector leaded out which can be plugged into proper female connector and in front there are mounting holes designed for placing brackets in form of spacers. All create compact construction and it won’t take to much place in a target device.
Because of the fact that our company released full technical documentation of own modules including schemes, anyone can easily look at our solutions and use them in their own. So our modules are designed mainly for those who eventually don’t have technologies and possibilities to prepare them in so small sizes, at home and meanwhile there is necessity of miniaturization of own projects, devices etc. Our primary goal is to provide knowledge about microcontrollers programming and for that it is worth to use similar technical solutions to understand exactly the discussed programming codes e.g. from books recommended by our publishing house.
Important parameters of the module are described in the table at the end of this page, in spite of this it is worth to pay attention on the fact that we used here our standard approach namely possibility of cooperation of the module in different voltage ranges if we are talking about a target circuit. So the module can be easily used in projects where a microcontroller is powered by +5V voltage (TTL levels) and also at +3,3V power. For that a user gets a jumper thanks to which he can easily chose demanded voltage level. On the module board there is specialized three-state buffers 74LVC125 that ensure proper voltage matching and at the same time it allows to get full speed on SPI bus during communication of a microcontroller with a card, what usually is not possible when using a circuit with resistor dividers popular on Internet and used in competitive modules. That is one of the most important factors of frequent transmission hang up when beginners that want to adjust voltages using what they have on their hand and what they see in Internet or in competitive modules they use the resistor dividers, The 74LVC125 ensures the best quality of signals edges on SPI lines what results in transmission reliability.
The discussed functionality was made (what can be seen on the scheme) using SMD PNP transistor which CE collector current must be higher than 100mA because of memory card needs. In this case we used BC807W (500mA). For convenience a control input leaded to the transistor base through a resistor was placed next to GND pin. So you can short these two pins if we do not want to use from the discussed function. In other case we connect to PWR pin directly to any I/O port of microcontroller. It is very important here to select proper values of power filter capacitors but also their arrangement on PCB to assure absolutely trouble-free memory card work. We should also remember to do not connect an electrolytic or a tantalum capacitor between a collector of the transistor and a memory card socket power pin. This would have a negative effect on time of card rest through the microcontroller. It would be drastically increased. We can only let ourselves for a ceramic capacitor 100nF but full reset time would be 400 ms. Regarding this above control procedures of card power supply should be carefully thought out. Not only the time of system switching off is very important but also disconnection of high state from all SPI lines in this time. Fortunately in the mentioned book an author very carefully prepared even separate programming libraries allowing for successful realization of this and also described everything precisely. Thanks to this , with our module and software even beginner will be able to create reliable working device in which the memory cards will be used. No more unforeseen hang ups, data or communication loss during the entire system work.
|Cards supported||all microSD|
|Power control||AUTO or from a processor|
|SPI line voltage range||+5V (TTL) or +3,3V|
|Power supply selection||JUMPER (5V/3,3V)|
|Stabilizer built n||+3,3V (LM1117)|
|Read out signalization||LED diode|
|PINs||Gold pin header|
|PCB pins description||YES|
|Mounting holes||YES ( 2x3,2 mm )|