PRO MIDI 1284P developer's board - Open Electronics

We develop and take a look at functions with the Professional midi 1284P board.

Lately now we have launched and described a brand new prototyping board known as PRO midi 1284, primarily based on an ATmega 1284P microcontroller; after this presentation, made in a earlier put up, we begin to work with it and we clarify the right way to interface it in a sensible and speedy strategy to the exterior world, at the least by way of {hardware}. For this function, on this article, we’ll suggest what, within the perspective of the event platform, is its pure complement, that could be a board created to permit and facilitate the research, improvement and debugging of functions primarily based on it. The board in query is the PRO midi 1284P Developer’s Board proven in Fig. 1.

This board gives a housing for the “PRO midi 1284P” and a complete sequence of connectors to attach or host varied digital units (additionally within the type of a breakout board) that permit you to develop functions that exploit the assorted sources of the Atmega1284P, akin to analogue ports, digital ports, serial ports, I²C bus, SPI bus, and so forth., and so forth..

Fig. 1.

Not solely that, for many who wish to develop in an MPLAB X setting and carry out each the code loading and the actual debugging, there’s additionally a JTAG connector the place to attach a budget SNAP programmer/debugger from Microchip; on this regard, we level out that the board, accessible from Open Electronics (additionally on-line at www.open-electronics.org) is already assembled however with the 2 LEDs LD1 and LD2 not soldered, however current within the package deal. Those that usually are not considering utilizing the MPLAB X improvement setting and the JTAG programmer/debugger, however intend to make use of the Arduino setting and programming by way of a serial port by way of the bootloader, can simply solder these LEDs (respecting the polarity, cathode on the left, anode on the appropriate, wanting on the board with the ability connector on the left). Alternatively, if you wish to use JTAG programming and debugging, it will be higher to keep away from soldering these LEDs, since they correspond to the TCK and TMS pins of the JTAG connector and will intervene with right operation.

ELECTRICAL DIAGRAM

On the prime you’ll be able to clearly see the ability provide part with the enter (blackjack, prime left of the board), the place you’ll be able to apply a voltage from 7V DC to 12V DC, related first to a 5V voltage regulator after which to a 3.3V voltage regulator. These two voltage regulators present the 2 respective voltages to all the board.

Notice that since a number of units will be related to the board and the ability consumption will be fairly excessive, the next limitations should be utilized, in any other case some elements could also be broken.

Don’t energy the “PRO midi 1284P Developer’s Board” by way of the USB <-> serial adapter current on the “PRO midi 1284P”, however solely by way of the black Jack. Which means that, for those who use Arduino IDE to program the MCU and also you interface by way of serial with an adapter, you could join all pins, besides the +Vcc pin (so you could join: GND, TX, RX and RST/DTR, however not +Vcc).
Restrict the whole absorption (+5V along with +3.3V) to a most of 1,000 mA. Larger absorptions might trigger the 5V regulator to overheat, leading to potential injury.
The ability provide coming to the MCU is +5V, so all direct I/Os of the Atmega1284P will likely be with that voltage. There are already some connectors on the board which have degree translators from 5V to three.3V (for instance for the I²C pins).

Slightly below the ability provide part, on the left aspect, you’ll be able to see two MOSFETs (Q1 and Q2) which have the duty to behave as degree shifters, between +5V and +3,3V, for the alerts going to the I²C bus and to some connectors already ready for a selected use, such because the one to attach a breadboard with a BMP180 sensor (temperature, humidity and atmospheric strain) or these to attach a 0.96″ OLED show (there are two variations of the 0.96″ OLED show and one has the ability pins reversed in comparison with the opposite, so you must be very cautious during which connector to insert the show).

One other connector permits the connection of different I²C units working at 3.3V, in truth, it makes accessible the GND pin, the +3.3V pin and the 2 SCL and SDA pins related to the extent shifter MOSFETs.

Notice that pull-up resistors for the I²C bus are already current on the board and are related to the SDA and SCL pins of the MCU (pin 16 and 17 of the “PRO midi 1284P” board).

Persevering with downwards, all the time on the left aspect of the diagram, we discover another connectors. Two of them enable the connection of I²C units working at 5V, whereas the final one on the backside is ready for the insertion of a breadboard with the RTC DS3231 module.

Within the centre of the diagram, there’s the MCU (ATmega1284P microcontroller) that’s mounted on the PRO midi 1284P board and that should be inserted within the house reserved for it on the PRO midi 1284P Developer’s Board.

Persevering with to look at the diagram of the board, on the appropriate aspect of the MCU, continuing from prime to backside, we discover a connector marked NEOPIXEL, on which connector there are the ability provides, +5V and GND, in addition to pin D0 for use for connecting a strip of LEDs WS2812 or comparable, known as NeoPixel.

There may be additionally a connector labelled ANALOG that makes accessible the analogue inputs A1, A2 and A3 in addition to offering +5V and GND; this can be utilized to attach sensors that present an analogue sign output between 0V and +5V.

Within the wiring diagram now we have, then, a connector marked APA102; it makes accessible the ability provide line (+5V and GND), in addition to the 2 pins D7 and D5 that can be utilized to regulate a strip of LEDs APA102 each with the administration completely software program of the 2 needed alerts (Clock and Information), and delegating this administration to the SPI library with which these LEDs are managed at excessive pace.

Let’s proceed with the evaluation arriving at trimmer R5, related on one aspect to +5V and on the opposite to GND, with the cursor related to analogue enter A0. This trimmer can be utilized to be taught the operation of an analogue port, in truth, once you rotate the slider from proper to left, the worth returned by the operate analogRead (A0) of Arduino, will differ from 0 to 1023 in a proportional strategy to the worth of voltage current on that pin A0.

A connector marked “SPI” that makes accessible the MOSI (D5), SCK (D7), MISO (D6) and SS (D4) pins, along with the same old +5V and GND, to attach objects that discuss to the microcontroller by way of the SPI bus. If you don’t use the SPI bus, a few of these pins can be utilized with the “Servo” library to drive servomotors. Within the latter case, we suggest that you simply seek the advice of Desk 1, which reveals the correspondence between the inner timers and their contacts on the board.

Desk 1

The circuit has two pushbuttons named P1 and P2, full with R/C debouncing community, related respectively to digital inputs D15 and D14; for his or her use take into account that these buttons are near the bottom (LOW worth of Arduino). In an effort to use them, they should be outlined in this system as inputs with an energetic pull-up resistor, or, utilizing the Arduino syntax, you could make the: pinMode(pin, INPUT_PULLUP) in order that, when the button shouldn’t be pressed, the enter could have a excessive worth (HIGH), whereas when the button is pressed, it would have a low worth (LOW).

Slightly below these buttons, within the diagram, we discover the JTAG connector. The use or not of such connector is a operate of the event setting that’s meant to make use of.

For many who will work in a pure Arduino setting, with using the IDE and programming by way of serial port, by way of using the exterior converter USB <-> Serial, and the “bootloader” current within the “PRO midi 1284P”, this JTAG connector will serve solely to have accessible pins D18, D19, D20 and D21 along with the RESET pin and energy provide, +5V and GND.

For many who will work within the MPLAB X setting of Microchip, this JTAG connector will make accessible all of the alerts for using a programmer/debugger as SNAP, that’s, along with the ability provide +5V and GND, additionally the alerts of TCK, TDI, TMS and RESET. Notice that the connector on the board is straight connectable to the aforementioned SNAP programmer, with a straight 7-conductor cable for the reason that pin place is similar because the programmer connector.

Lastly, on the backside of the circuit below the JTAG connector, we discover 4 light-emitting diodes, recognized by the initials LD1, LD2, LD3 and LD4. As talked about earlier, solely the 2 LEDs LD3 and LD4 will likely be soldered on the board, whereas the remaining two LEDs, LD1 and LD2, will likely be equipped unsoldered. It is going to be as much as the end-user to decide on whether or not to depart solely two LEDs on the board or to mount all 4, relying on whether or not or not the JTAG programmer/debugger is used. In an effort to facilitate low-level programming, we present in Desk 2 the correspondence of among the pins used within the PRO midi 1284P Developer’s Board.

Desk 2

Fig. 2 reveals the association of the described connectors. The serigraphy on the board clearly signifies the that means of every single pin. As it’s clear from the provision of connectors each generic (SPI, I÷C, ANALOG, and so forth.) and particular (OLED Show, RTC DS3231, BMP180 module, and so forth.) the PRO midi 1284P Developer’s Board permits to make use of of all of the sources of the Atmega1284P and to be taught the use and programming of them permitting the experimentation on using varied extra {hardware} elements.

Fig. 2

Fig. 3 reveals the event board with the PRO midi 1284 and an RTC module put in; as a substitute in Fig. 4 you see the board utilized to an Arduino Mega (by advantage of the presence of the strips on the underside, which match the Arduino Mega headers), simply to provide you an concept of the flexibility of the event system that it varieties with the ProMidi 1284P.