PRO MIDI 1284P developer’s board – Open Electronics


We develop and check purposes with the Professional midi 1284P board.

Lately now we have launched and described a brand new prototyping board known as PRO midi 1284, based mostly on an ATmega 1284P microcontroller; after this presentation, made in a earlier submit, we begin to work with it and we clarify the way to interface it in a sensible and speedy method to the exterior world, a minimum of by way of {hardware}. For this objective, on this article, we are going to suggest what, within the perspective of the event platform, is its pure complement, that could be a board created to permit and facilitate the examine, growth and debugging of purposes based mostly on it. The board in query is the PRO midi 1284P Developer’s Board proven in Fig. 1.

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

Fig. 1.

Not solely that, for individuals who wish to develop in an MPLAB X surroundings and carry out each the code loading and the true 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, out there from Open Electronics (additionally on-line at is already assembled however with the 2 LEDs LD1 and LD2 not soldered, however current within the bundle. Those that should not all for utilizing the MPLAB X growth surroundings and the JTAG programmer/debugger, however intend to make use of the Arduino surroundings and programming through a serial port by the bootloader, can simply solder these LEDs (respecting the polarity, cathode on the left , anode on the precise, wanting on the board with the facility connector on the left). Then again, if you wish to use JTAG programming and debugging, it might be higher to keep away from soldering these LEDs, since they correspond to the TCK and TMS pins of the JTAG connector and will intrude with right operation.


On the prime you possibly can clearly see the facility provide part with the enter (blackjack, prime left of the board), the place you possibly can apply a voltage from 7V DC to 12V DC, linked first to a 5V voltage regulator after which to a 3.3V voltage regulator. These two voltage regulators present the 2 respective voltages to your complete board.

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

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

Slightly below the facility provide part, on the left aspect, you possibly can see two MOSFETs (Q1 and Q2) which have the duty to behave as stage shifters, between +5V and +3,3V, for the indicators 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 facility pins reversed in comparison with the opposite, so it’s important to be very cautious by which connector to insert the show).

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

Notice that pull-up resistors for the I²C bus are already current on the board and are linked to the SDA and SCL pins of the MCU (pins 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 middle 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 precise aspect of the MCU, continuing from prime to backside, we discover a connector marked NEOPIXELon which connector there are the facility provides, +5V and GND, in addition to pin D0 for use for connecting a strip of LEDs WS2812 or related, known as NeoPixel.

There’s additionally a connector labeled ANALOG that makes out there 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 facility 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 obligatory indicators (Clock and Knowledge) , and delegating this administration to the SPI library with which these LEDs are managed at excessive velocity.

Let’s proceed with the evaluation arriving at trimmer R5, linked on one aspect to +5V and on the opposite to GND, with the cursor linked to analogue enter A0. This trimmer can be utilized to study the operation of an analogue port, in reality, 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 method to the worth of voltage current on that pin A0.

A connector marked “SPI” that makes out there the MOSI (D5), SCK (D7), MISO (D6) and SS (D4) pins, along with the standard +5V and GND, to attach objects that speak to the microcontroller by 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 just seek the advice of Desk 1which 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, linked respectively to digital inputs D15 and D14; for his or her use needless to say these buttons are near the bottom (LOW worth of Arduino). To be able to use them, they should be outlined in this system as inputs with an energetic pull-up resistor, or, utilizing the Arduino syntax, you have to make the: pinMode(pin, INPUT_PULLUP) in order that, when the button is just not pressed , the enter may have a excessive worth (HIGH), whereas when the button is pressed, it should 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 surroundings that’s meant to make use of.

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

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


Lastly, on the backside of the circuit underneath 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 probably be soldered on the board, whereas the remaining two LEDs, LD1 and LD2, will probably be equipped unsoldered. It will likely be as much as the end-user to decide on whether or not to go away solely two LEDs on the board or to mount all 4, relying on whether or not or not the JTAG programmer/debugger is used. To be able 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 which 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 study the use and programming of them permitting the experimentation on using numerous further {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 present you an thought of ​​the flexibility of the event system that it kinds with the ProMidi 1284P .

Fig. 3

Fig. 4

Record of Elements:

R1, R2, R3, R4: 4.7 Kohm

R5: Trimmer 10 Kohm MV

R6, R7: 1kohm

R8, R9, R10, R11, R12: 470 ohms

C1, C7, C9: 100 F 35 VL Electrolytic

C2, C5, C6, C8: 100 nF Ceramic

C3, C4: 100 nF 100 VL polyester

LD1: 5mm LED inexperienced (see textual content)

LD2 LED 5 mm yellow (see textual content)

LD3 LED 5 mm crimson

LD4 LED 5mm inexperienced

P1, P2: Microswitch

Q1, Q2: BS170

BMP180: BMP180 module

OLED1: 0.96″ I2C . OLED show

LCD: I2C LCD show

DS3231: DS3231 RTC Module

SERVO: 6V . Servomotor




U1: 7805

U2: MCP1702-3302E/TO


– 3-way feminine strip (1 computer.)

– 4 methods feminine strips (7 pcs.)

– 5 methods feminine strip (1 computer.)

– 6 methods feminine strips (2 pcs.)

– 7 methods feminine strip (1 computer.)

– 20 methods feminine strip (2 pcs)

– 8 methods Arduino strips (5 pcs.)

– 10 methods Arduino strips (1 computer.)

– Arduino strips 2×18 methods (1 computer.)

– Energy provide plug

– PCB S1393 (102×73 mm)


Professional Midi 1284P

PRO midi 1284P Developer’s Board

1.3 inch OLED show

Breakout with DS3231 & EEPROM