nrf24l01模块售后资料wireless_keyboard_using_nrf24ex

1、WHITE PAPERnRF24Ex in a wireless keyboard design*(1(5$/With the nRF24E1 and nRF24E2, in this document called nRF24Ex, from Nordic VLSI ASA is it now possible to design a wireless keyboard for the 2.4GHz ISM band. The nRF24Ex series has an embedded 8051 microcontroller, a 9 channel ADC and the same R

2、F part as the popular nRF2401/nRF2402. The nRF24Ex series can run at voltages from 1.9V to 3.6V making it especially suited for battery applications. This white paper will show how a keyboard scan matrix can be realized by using the nRF24Ex.7+( (6,*1Keyboard Scan MatrixRow 0Row 1Row 2Row 3Row 4Row 5

3、Row 6Row 76KRFShift registerN%XUVWnRF24ExFigure 1 nRF24Ex in a wireless keyboard design7KH 5) SDUWAs shown in the schematics, Figure 4, the RF part is based on the nRF24Ex reference design that can be downloaded from www.nvlsi.no. The design has a 16MHz crystal and an external EPROM for firmware sto

4、rage. The firmware will use the ShockBurst technology to transmit the packets from the keyboard. The ShockBurst technology is designed to minimize the current consumption per transmitted bit in order to extend the battery lifetime. Read more about the ShockBurst technology in the nRF24Ex datasheet a

5、nd in a white paper that can be downloaded from www.nvlsi.no.Nordic VLSI ASA-Vestre Rosten 81, N-7075 Tiller, Norway3DJH RI-Phone +4772898900-Fax +4772898989October 2003Shift registerCol 0Col 1Col 2Col 3Col 4Col 5Col 6Col 7Col 8Col 9Col 10Col 11Col 12Col 13Col 14Col 15Col 16Col 17Col 18Col 19WHITE P

6、APERQ5) ( LQ D ZLUHOHVV NHERDUG GHVLJQ:LUHOHVV NHERDUG EDVLFVWireless keyboards are using RF to communicate with the PC. They are mostly powered by batteries, and as a consequence of this, some power saving techniques are used. The LEDs that indicate “Num Lock”, “Caps Lock” and “Scroll Lock” on wire

7、d keyboards are not present on wireless keyboards. This is one of the power saving actions that has been taken on wireless keyboards.Careful use of the RF module is another power saving technique. A RF data packet from the keyboard to the PC can contain up to 8 key strokes. The scan matrix is scanne

8、d about 500 times pr second. Normally not more than one keystroke is detected during one scan period. Humans will not detect delays that are shorter than 150ms, so if the keyboard detects a keystroke, it can wait up to 150ms to collect even more keystrokes before transmitting a packet to the PC. Thi

9、s will ensure as little use of the RF module as possible.A keyboard using the nRF24E2 will only be able to send data to the PC. This will give enough features for most keyboard vendors. If a two-way link is required, the nRF24E1 should be used. The keyboard will then be able to receive data from the

10、 PC. This opens for features like link encryption, retransmission protocol and even more power saving features like detection of system power off.HERDUG VFDQ PDWULA keyboard can have as many as 104 keys that are organized in a scan matrix. The scan matrix can have 8 rows and up to 20 columns. This e

11、nables a maximum of 160 unique keys to be placed on a keyboard. Each key is connected to an intersection between a row and a column, as shown in Figure 2. When pressed, the key will connect the row with the column in that intersection.VccRow 7Row 6Row 5Row 4Row 3Row 2Row 1Row 0Figure 2 Key connectio

12、nTo scan the matrix, the nRF24Ex will clock a bit pattern into the column shift register (see Figure 4 for details.) This bit pattern consists of one 0 and nineteen 1s. The 0 isNordic VLSI ASA-Vestre Rosten 81, N-7075 Tiller, Norway3DJH RI-Phone +4772898900-Fax +4772898989October 2003Col 0Col 1Col 2

13、Col 3Col 4Col 5Col 19WHITE PAPERQ5) ( LQ D ZLUHOHVV NHERDUG GHVLJQshifted trough the shift register. For each time the 0 is shifted one position, the rows are read. If a key has been pressed on the column being set to 0 at that point, a 0 will come out on the intersecting row. See Figure 3 for detai

14、ls.VccRow 711111Row 611111Row 511111Row 411111Row 311011Row 211111Row 111111Row 011111Pattern 0Pattern 1Pattern 2Pattern 3Pattern 401111111101101111111111101111111011Figure 3 Key press detectionKeys that are pressed may bounce and cause misdetection of real key events. To solve6FKHPDWLFVFigure 4 sho

15、ws how the 74HC595 and 74HC597 shift registers together with the standard nRF24Ex layout with an EPROM, can be interfaced to a keyboard scan matrix.Nordic VLSI ASA-Vestre Rosten 81, N-7075 Tiller, Norway3DJH RI-Phone +4772898900-Fax +4772898989October 2003Result 4Result 3Result 2Result 1Result 0Col

16、0Col 1Col 2Col 3Col 4Col 5Col 19WHITE PAPERQ5) ( LQ D ZLUHOHVV NHERDUG GHVLJQ? ?U6 KEYBOARDSCANRow 78Row7Row6Row5Row 67Row 56VDDRow 45Row4Row3Row 34U5Row 2391087Row2Q GNDMR D7SH_CP D6ST_CP D5PLD4DSD3D0D2Vcc D1Row 7Row 12116Row 6Row1Row0121354Row5Row4Row 01141532Row3Row2161Row 174HC597Row 0R5 10KRowD

17、ataU2U3U4VDDVDDR222kR14 10KR15 10KC51nFC610nFVDD1234272625242322VDD AIN0 DVDD2 P1.0P1.1 P0.0 P0.1 P0.2 P0.3IREF AIN5 AIN6 AIN7VSS VDD VSS_PA ANT2 ANT1C7 10nFC8nRF24E11nFRowData RowClockC125678212019RowLatch PL1.0pFL1 3.6nH9C13 1.5pFColDataColLatch ColClockC11OE1.0pFU1 nRF24E1L2 22nHVDDR3 10KAnt1PCB

18、AntennaU2VDDX1C3C412387CS SO WP VSS VCC HOLDSCK SI2.2nF22pF6C14C9C10 33nF4510nF1nF16 MHzR125XX320R6 10K1MC1 15pFC2 15pFFigure 4 Schematics of the nRF24EX Wireless KeyboardNordic VLSI ASA-Vestre Rosten 81, N-7075 Tiller, Norway-Phone +4772898900-Fax +4772898989October 20033DJH RI101112131415161718363

19、534333231 302928P0.4 P0.5 P0.6 P0.7 DVDD VSS XC2 XC1VDD_PAP1.2 AIN1 AIN2 VSS VDD VSS AIN3 AIN4 AREF Col 0 9 Col 1 10Col 0Col 1 Col 2 11Col 2 Col 3 12Col 3 Col 4 13Col 4 Col 5 14Col 5 Col 6 15 Col 7 16876543219 Q7 GNDCol 610 MRCol 7Col 6Col 5Col 4Col 3Col 2Col 1Q711 SH_CP Q6Col 712 ST_CP Q5 Col 8 171

20、3 OE14 DS15 Q016 VccQ4 Q3 Q2 Q1Col 8 Col 9 18Col 9 Col 10 19Col 1074HC595Col 0 Col 11 20Col 11 Col 12 219 Q7 GND87654321Col 1210 MRCol 15Col 14Col 13Col 12Col 11Col 10Col 9Q7 Col 13 2211 SH_CP Q6Col 1312 ST_CP Q5 Col 14 2313 OE14 DS15 Q016 VccQ4 Q3 Q2 Q1Col 14 Col 15 24Col 15 Col 16 25Col 1674HC595C

21、ol 8 Col 17 26Col 17 Col 18 27876543219 Q7 GND10 MRCol 18Q7 Col 19 2811 SH_CP Q612 ST_CP Q5Col 1913 OE14 DS15 Q016 VccQ4 Q3 Q2 Q1 Col 19 Col 18 Col 1774HC595Col 16OEColLatchColClockColDataPLRowLatchRowClockWHITE PAPERQ5) ( LQ D ZLUHOHVV NHERDUG GHVLJQ667(0 ),50:$5(The nRF24Ex has 4K of internal RAM

22、used for firmware storage. It is more than enough space for the keyboard firmware.The firmware should perform the following tasks: Load scan shift registers with scan patternsRead scan rowsDetect and de-bounce key pressesSend the key press scan codes to the PC Power duty cyclingAs mentioned earlier

23、in this document the wireless keyboard should use power saving techniques to extend battery lifetime. Low power consumption when operating the radio is given by the ShockBurst technology, so the system firmware designer does not have to worry about that. But the average system standby current can be

24、 further reduced by implementing power duty-cycling techniques.The nRF24Ex dra3mA when the 8051 core is running. Since the use of a keyboardis periodically with long delays between use, a lot of current can be saved by puttingthe 8051 core in power down when the keyboard is not used. The current con

25、sumption in power down mode is 2uA.A typical power duty cycling algorithm can have two operating modes; Idle and Active mode.Idle mode: Perform a complete keyboard scan. (takes 0.5 ms)If a key has been pressed, go to active mode.Set 8051 in power down with RTC wakeup enabled on 20 ms. Loop idle mode

26、.Active mode: Scan the keyboard 500 times/second.Send any key pressed scan codes to the PC.If no key pressed in 10 seconds, go to idle mode.Loop active mode.This power duty cycling will reduce the average stand-by current consumption from 3mA to (0.5ms*3mA+2uA*20ms)/20.5ms = 75uA. This will cause th

27、e batteries to last 40 times longer!Fax +4772898989October 2003Nordic VLSI ASA-Vestre Rosten 81, N-7075 Tiller, Norway3DJH RI-Phone +4772898900-WHITE PAPERQ5) ( LQ D ZLUHOHVV NHERDUG GHVLJQ/,$%,/,7 ,6&/$,0(5Nordic VLSI ASA reserves the right to make changes without further notice to the product to i

28、mprove reliability, function or design. Nordic VLSI does not assume any liability arising out of the application or use of any product or circuits described herein./,)( 6833257 $33/,&$7,216These products are not designed for use in life support appliances, devices, or systems where malfunction of these products can reasonably be expected to result in personalinjury. Nordic VLSI ASA customers using or selling these products for useuchapplications