|Voltage||5 V||Voltage on JP1. On the USB connector the max voltage is 5 V. Absolute max voltage is 9 V for shorter periods|
|Current||70 mA, 1)|
110 mA, 2)
500 mA, 3)
|1) No LCD or GPS antenna connected. Program with empty setup and loop
2) Beacon program with LCD and GPS antenna connected
3) Maximum total current
|Supply connector||2 pin terminal block||Ø1 mm wire|
|GPS connector||SMA female||3,3 V DC to GPS pre-amp. Optional GPS USB connection on bottom side|
|RF power||13 dBm||400 kHz to 200 MHz|
|RF clock||27 MHz, 10 PPM|
|RF connector||SMA female|
|USB connector||USB B female|
|Micro controller||ATSAMD21G18||32 bit ARM Cortex M0+|
|MCU clock||48 MHz, 10 PPM|
|Flash memory||256 kB|
|EEPROM||1 kB||Changeable. 8 pin DIP in socket|
|DC current per I/O pin||7 mA|
|MCU connector||10 pin Cortex||2 x 5 pin 50 mil connector|
|Analog inputs||8||12 bits|
|Analog output||1||10 bits|
|Digital I/Os||28||Hereof up to eight can be analog|
|Driver||ULN2803A||8 bit Darlington array 50 V and 500 mA. In socket for easy replacement|
|PWM pins||16||Pins D0-D11 and A2-A5 on TCC0/1/2 and TC3|
|I2C, SPI and UART ports||3, 4, 4||SERCOM ports|
|LCD connector||SIL 12 pin 2,54 male||Pin 1-6 to LCD pin 1-6 (VSS-E), and pin 7-12 to LCD pin 11-16 (DB4-Cathode)
Not factory mounted
|LCD voltage jumper¹||SIL 3 pin 2,54 male||3,3 V or VI that is about 0,5 V below the supply connector or USB voltage whichever is highest. Not factory mounted|
|Headers||SIL 2,54 mm male||Not factory mounted|
|Ground loop||Ø1,5 mm cobber wire||Not factory mounted|
|LEDs||3 mm||Five LEDs. Not factory mounted|
|Size||99,5 mm x 79 mm||Half Eurocard PCB. Fits into a standard metal sheet box (Weissblechgehäuse) 102 mm x 82 mm x 30 mm for optimum RF shielding|
¹: The LCD can be supplied either by 3,3 V or VI using the JP13 jumper. But the control and data lines are always 3,3 V logic. Different contrast and backlight values apply. The backlight can be increased by adding a blob of solder to the SJ1 solder joint shorting the R16 backlight resistor.
The reason for not factory mounting the LEDs and headers is to allow for individual configuration e.g. mounting the LEDs through a front plate and only install the relevant jumpers/headers.
The RFzero can use both 3,3 V and 5 V liquid crystal displays (LCD), but, if using a 5 V LCD the logic communication has to work on 3,3 V level. Most modern 5 V LCDs are able to do this but if you have an old 5 V LCD it may not work. If you are to buy a new LCD please ask the seller specifically for a 3,3 V LCD.
RFzero, and Arduino in general, supports LCDs that are compatible with the Hitachi HD44780 specification. You can use other standards but in this case you may have to find a third party display library or write it yourself.
LCD voltage jumper
Before you connect any LCD to the LCD header please ensure you have set the correct drive voltage for the LCD on the LCD voltage select header – JP13. Alternatively, if you know that you will always be using one of the voltages you could short the relevant jumper position with a small piece of wire that is soldered in place.
The LCD voltage header JP13.
The LCD voltage set to use VI
Please note that if you run the LCD on the VI level the contrast and backlight will change if the VI is changed.
The LCD voltage set to use 3,3 V (3V3).
LCD header and connections
The RFzero LCD header JP12 is prepared for LCDs that comply with the Hitachi HD44780 specification. Using two cables with six wires in each you can easily connect the LCD to the RFzero board. One cable should go to the left side of JP12 (GND, V LCD, CON, RS, R/W and ENA) and the other cable to the right side of JP12 (DB4, DB5, DB6, DB7, Anode and Cathode).
The LCD header JP12.
On the backside of the LCD connect the two cables to “each end” of the 16 pads/pin header leaving the four in the middle unused.
Two six wire cables connected to a LCD pins 1-6 and 11-16.
The RFzero LCD header is designed to run the LCD in four bits mode, i.e. LCD data on D7 to D4. If you need to run your LCD in eight bits mode you will have to take the remainder four bits from some of the other pins available on the RFzero and connect them to the D3 to D0 pins on the LCD.
LCD contrast and backlight
The contrast of the LCD can be controlled on the R15 trimmer. Please note that if you run the LCD on the VI level the contrast will change if VI is changed.
If you think that the backlight is not strong enough for the place where you will use your RFzero you can add a blob of solder to the SJ1 solder jumper. Doing so shorts R16 so the backlight resistor goes from 20 Ω to 10 Ω allowing more current to the LCD.
The R15 LCD contrast trimmer and SJ1 solder jumper.
Please note that if you run the LCD on the VI level the backlight will change if the input voltage is changed.
Debugging, test points and GPS USB
The RFzero board contains a number of test points that can be used for troubleshooting or optional access. Keep in mind that you can also use the Test LED as an aid in the software debugging.
|TP1||VI (about 0,5 V below the supply voltage)||~4,5 V if supplied from 5 V or USB||Analog|
|TP2||Voltage on the digital circuit||3,3 V||Analog|
|TP3||Voltage on the Si5351A||3,3 V||Analog|
|TP4||USB DP||USB serial data||Digital|
|TP5||USB DM||USB serial data||Digital|
|TP6||GPS data out (TX, GDO)||Serial data||Digital|
|TP7||GPS control data in (RX, GCI)||Serial data||Digital|
|TP8||GPS PPS (GPO)||One pulse per second and 100 ms wide (default)||Digital|
|TP9||GPS pre-amplifier voltage||3,3 V||Analog|
|TP10||I2C/Wire internal SCL||Serial data to/from the EEPROM and Si5351A||Digital|
|TP11||I2C/Wire internal SDA||Serial data to/from the EEPROM and Si5351A||Digital|
|TP12||Ground on bottom side of the PCB||Ground||Analog|
|TP13||Optional GPS USB DP on the bottom side of the PCB||USB serial data to/from the GPS||Digital|
|TP14||Optional GPS USB DM on the bottom side of the PCB||USB serial data to/from the GPS||Digital|
The TP12, TP13 and TP14 test points on the bottom side can be used to access the u-blox NEO-7M directly via an USB port, e.g. for synchronizing a PC to the GPS network. By default this optional GPS access is disabled. To enable it simply short the SJ2 solder jumper on the bottom side.
The bottom side of the PCB showing the optional GPS solder points where G = Ground, M = DM, P = DP and the SJ2 solder jumper (square pads).
Pin outs, schematic and component locations
An on-board low/high pass filter can be designed using the free Elsie by Tonne Software Jim, W4ENE. It is a highly recommended filter design program that you can use to design your own RFzero low/high pass filter if relevant.
If you want to expand the RFzero board with your own circuit you can easily add a shield that covers the analog and digital MCU pins found on JP2: GND and VI, JP3: USB, JP4: A0-A5, JP5/JP6: D0-D7, JP10: D16-D19, JP11: D8-D15, and JP12: LCD.
The size of the shield should be slightly larger than 19 modules x 24 modules (~50 mm x ~63 mm) to make a perfect fit.
You can make your own shield from a standard Vero-board.
If you have a shield mounted on your RFzero and want to access the GPS module you can do this via JP12. You may even connect several shields by daisy chaining the RFzero GPS Data Out (GDO) to the next GPS Data In (GDI) and GPS PPS Out (GPO) to the next GPS PPS In (GPI) and GND to GND too. This easiest way to do this is to use three-wire jumper cables jumping form board to board.
In the RFzero library the Feedback Multisynth Divider variables are named a, b and c, just like in the datasheet/programming guide. However, the Output Multisynth Divider variables are named d, e and f instead of a, b and c to make the code easier to distinguish.
The Coilcraft PWB-2-BLB transformer is the default T1 component.