AN_371 FT90x WS2812 Example
Contents
1. sssssssusu2u222 2 n 7 3 3 Main APDiCAtiON iisiciisssscriertssieieuresietretintiestabiiereieaie erie 8 4 CONCUSSION ei E EE EEA 10 5 Contact Information pivauowsaaswes oninia Doene anioia 11 Appendix A References ssss EEE 12 Document RefEreNnCes cccceeeeeeeeeeeeeeeeeeee eee 12 Acronyms and ADDreviatiONnsS ccccsssccccccnneescccnneeeseeenneseseennnenesoss 12 Appendix B List of Tables amp Figures ccsssssceeennnesees 13 LIGCOF TADS isinisisi aA 13 LISE OF FIQGUIES siicicssaricietcntrsdedcereciniestirdrenstitisassrirdercatesdbeetecinbeens 13 Appendix C Revision HIStOPy cccssessseeeennnsseseeennneeees 14 1 Product Page Document Feedback Copyright 2015 Future Technology Devices International Limited h Application Note FTDI AN_371 FT90x WS2812 Example Chip Version 1 0 Document Reference No FT_001166 Clearance No FTDI 446 1 Introduction This Application Note describes and explains the FT90x WS2812 Example The FT90x WS2812 Example demonstrates how to interface with the World Semi WS2812 Intelligent control LED integrated light source with an FT90x microcontroller 1 1 Overview This document will describe the design and implementation of the FT90x WS2812 Example The FT90x WS2812 Example will control two WS2812 LEDs on a MM900 Evaluation Board and fade them through various hues WS2812 LEDs use a proprietary 1 Wire like protoco2. FTDI Chip N d Application Note AN_371 FT9Ox WS2812 Example Version 1 0 Issue Date 2015 10 06 This note describes how to use GPIO to communicate with the WS2812 Intelligent control LED integrated light source on the MM900 EV Module Use of FTDI devices in life support and or safety applications is entirely at the user s risk and the user agrees to defend indemnify and hold FTDI harmless from any and all damages claims suits or expense resulting from such use Future Technology Devices International Limited FTDI Unit 1 2 Seaward Place Glasgow G41 1HH United Kingdom Tel 44 0 141 429 2777 Fax 44 0 141 429 2758 Web Site http ftdichip com Copyright 2015 Future Technology Devices International Limited y E Application Note FTDI AN_371 FT90x WS2812 Example Chip Version 1 0 Document Reference No FT_001166 Clearance No FTDI 446 a Table of Contents L TRCPOGUCCION sccscucciccacrnveccsvestusecnrcreecsssasiseaveevecasuestisec 2 LL OV CEVICW oiro acoenreiniaiwenteiaineiereeeeunEn 2 1 2 LICENSE setandvextucwcnsusneuencsesovceav she venceancueuasavasehaudseuckeueneuencesanenc 2 2 e icacdececasadecetenscesnsucsdecriuctcsarvacudvaniusadeareieudusncasvens 3 2l WOZGRZ MEDS iorns rhinn NENEI 3 3 Implementation ss 2 2525202222222222 25202u2u2 2 2 2 2 n D 3 1 Bit banging the WS2812 Protocol via GPIO ssssss2s 5 3 2 HSV to RGB Colour Space Conversion
3. by FTDI Use of FTDI devices in life support and or safety applications is entirely at the user s risk and the user agrees to defend indemnify and hold harmless FTDI from any and all damages claims suits or expense resulting from such use This document is subject to change without notice No freedom to use patents or other intellectual property rights is implied by the publication of this document Neither the whole nor any part of the information contained in or the product described in this document may be adapted or reproduced in any material or electronic form without the prior written consent of the copyright holder Future Technology Devices International Ltd Unit 1 2 Seaward Place Centurion Business Park Glasgow G41 1HH United Kingdom Scotland Registered Company Number SC136640 13 Product Page Document Feedback Copyright 2015 Future Technology Devices International Limited Application Note FTDI AN_371 FT90x WS2812 Example Chie Version 1 0 Document Reference No FT_001166 Clearance No FTDI 446 d Appendix A References Document References FT900 901 902 903 Datasheet FT905 906 907 908 Datasheet FT900 User Manual World Semi WS2812 Intelligent control LED integrated light source Datasheet Acronyms and Abbreviations GPIO General Purpose I O HSV Hue Saturation Value LED Light Emitting Diode RGB Red Green Blue 14 Product Page Document Feedback Copyright 2015 Future Technol
4. for the GPIO pin defined in WS2812_GPIO e A loop iterates over every bit in parameter b starting at Most Significant Bit and working down to the Least Significant Bit e Within the loop the corresponding symbol mask is chosen and bit banged out on the GPIO pin NOOP instructions are used to generate the precise timing void ws2812_shiftout uints t b uint8 t i register uint8_t sym 0 sym WS2812_GPIO_SYMO sym1 WS2812_GPIO_SYM1 register uint32_t mask register volatile uint32_t gpioval if WS2812 GPIO lt 32 31 gpioval amp GPIO gt GPIO 31 VAL mask 1 lt lt WS2812 GPIO elif WS2812 GPIO lt 64 32 63 gpioval amp GPIO gt GPI032_63_VAL mask 1 lt lt WS2812 GPIO 32 else 64 66 gpioval amp GPIO gt GPI064 66 VAL mask 1 lt lt WS2812 GPIO 64 endif for i O i lt 8 i if b amp 0x80 sym else sym sym1 sym if sym amp 0x80 gpioval mask else spioval amp mask asm _noop asm _noop asm _noop asm _noop if sym amp 0x40 gpioval mask else spioval amp mask asm _noop asm noop asm _noop if sym amp 0x20 gpioval mask else spioval amp mask asm _noop asm _noop asm _noop asm _noop if sym amp 0x10 gpioval mask else spioval amp mask asm _noop asm _noop asm _noop if sym amp 0x08 gpioval mask else spio
5. ce Shanghai China Future Technology Devices International Limited Future Technology Devices International Limited Taiwan China 2F No 516 Sec 1 NeiHu Road Room 1103 No 666 West Huaihai Road Taipei 114 Shanghai 200052 Taiwan R O C China Tel 886 0 2 8791 3570 Tel 86 21 62351596 Fax 886 0 2 8791 3576 Fax 86 21 62351595 E mail Sales tw sales1 ftdichip com E mail Sales cn sales ftdichip com E mail Support tw supporti ftdichip com E mail Support cn support ftdichip com E mail General Enquiries tw admini ftdichip com E mail General Enquiries cn admin ftdichip com Web Site http ftdichip com Distributor and Sales Representatives Please visit the Sales Network page of the FTDI Web site for the contact details of our distributor s and sales representative s in your country System and equipment manufacturers and designers are responsible to ensure that their systems and any Future Technology Devices International Ltd FTDI devices incorporated in their systems meet all applicable safety regulatory and system level performance requirements All application related information in this document including application descriptions suggested FTDI devices and other materials is provided for reference only While FTDI has taken care to assure it is accurate this information is subject to customer confirmation and FTDI disclaims all liability for system designs and for any applications assistance provided
6. ent Feedback Copyright 2015 Future Technology Devices International Limited Application Note FTDI AN_371 FT90x WS2812 Example Chip Version 1 0 Document Reference No FT_001166 Clearance No FTDI 446 4 Conclusion The FT90X devices make for an ideal controller in a home automation or advertising application where the control of multiple LED lighting is required The GPIO interface allows for a relatively simple coding exercise to realize full colour and brightness control of the LEDs 12 Product Page Document Feedback Copyright 2015 Future Technology Devices International Limited Application Note FTDI AN_371 FT90x WS2812 Example Chie Version 1 0 Document Reference No FT_001166 Clearance No FIDI 446 A 5 Contact Information Head Office Glasgow UK Branch Office Tigard Oregon USA Future Technology Devices International Limited Future Technology Devices International Limited Unit 1 2 Seaward Place Centurion Business Park USA Glasgow G41 1HH 7130 SW Fir Loop United Kingdom Tigard OR 97223 8160 Tel 44 0 141 429 2777 USA Fax 44 0 141 429 2758 Tel 1 503 547 0988 Fax 1 503 547 0987 E mail Sales sales1 ftdichip com E mail Support supporti ftdichip com E Mail Sales us Sales ftdichip com E mail General Enquiries admini ftdichip com E Mail Support us Support ftdichip com E Mail General Enquiries us admin ftdichip com Branch Office Taipei Taiwan Branch Offi
7. ices International Limited Application Note AN_371 FT90x WS2812 Example Version 1 0 Document Reference No FT_001166 Clearance No FIDI 446 Table 5 Code Listing for Function hsv2rgb 3 3 Main Application This application shown in Table 6 Code Listing for the Main Application will fade the two WS2812 LEDs on the MM900 board through different hues with one LED having the opposite hue of the other LED int main void setup for loop return void setup uint8 t i for i 0 i lt N_LEDS i Every LED has a different Hue Offset ledhsv i hue 255 N_LEDS i ledhsv i val VALUE ledhsv i sat SATURATION wS2812 init void loop uint8 t i Fade to a new colour for i 0 i lt N_LEDS i hsv2rgb ledhsv i hue ledhsv i sat ledhsv i val amp ledrgb i r amp ledrgb i g amp ledrgb i b ledhsv i hue 10 Product Page Document Feedback Copyright 2015 Future Technology Devices International Limited Application Note AN_371 FT90x WS2812 Example Version 1 0 Document Reference No FT_001166 Clearance No FIDI 446 Write the new values to the LEDs for i 0 i lt N_LEDS i ws2812 write ledrgb i r ledrgb i g ledrgb i b delayus 5 Have to wait this much for the WS2812 to latch their colour delayms 25 Table 6 Code Listing for the Main Application 11 Product Page Docum
8. l to shift in colour values and allow data to be daisy chained to other WS2812 LEDs This document is intended to demonstrate the bridging capabilities of the FT90x family of microcontrollers 1 2 License Copyright 2015 Future Technology Devices International Ltd This source code the Software is provided by Future Technology Devices International Limited FTDI subject to the license terms set out http www ftdichip com FTSourceCodeLicenceTerms htm the License Terms You must read the License Terms before downloading or using the Software By installing or using the Software you agree to the License Terms If you do not agree to the License Terms then do not download or use the Software Without prejudice to the License Terms here is a summary of some of the key terms of the License Terms and in the event of any conflict between this summary and the License Terms then the text of the License Terms will prevail The Software is provided as is There are no warranties or similar in relation to the quality of the Software You use it at your own risk The Software should not be used in or for any medical device system or appliance There are exclusions of FTDI liability for certain types of loss such as special loss or damage incidental loss or damage indirect or consequential loss or damage loss of income loss of business loss of profits loss of revenue loss of contracts business interruption loss of the use of m
9. oL O code Low Voltage Time 550 700 850 tin 1 code High Voltage Time 650 800 950 ti 1 code Low Voltage Time 450 600 750 Table 1 Timing for WS2812 Symbols 4 Product Page Document Feedback Copyright 2015 Future Technology Devices International Limited Application Note FTDI AN_371 FT90x WS2812 Example Chip Version 1 0 Document Reference No FT_001166 Clearance No FTDI 446 Colour is transferred to a WS2812 LED in 24 bit chunks an 8 bit value of Green an 8 bit value of Red and an 8 bit value of Blue Most Significant Bit first Multiple colours can be transferred in order to update multiple LEDs At the end of an update a Reset must be sent which will cause the LEDs to latch in the new colour LED 1 LED 2 LEDN Reset Figure 2 Timing Diagram for WS2812 Update 5 Product Page Document Feedback Copyright 2015 Future Technology Devices International Limited h Application Note FTDI AN_371 FT90x WS2812 Example Chip Version 1 0 Document Reference No FT_001166 Clearance No FTDI 446 3 Implementation 3 1 Bit banging the WS2812 Protocol via GPIO Several methods of communicating with WS2812 are available UART SPI GPIO however for the purposes of this demo GPIO was selected In order to simplify transferring bits to the WS2812 a common symbol time for 1 s and O s is derived and separated up into 8 sections to allow the use of an 8 bit long pattern The du
10. ogy Devices International Limited
11. oney or anticipated savings loss of information loss of opportunity loss of goodwill or reputation and or loss of damage to or corruption of data There is a monetary cap on FTDI s liability The Software may have subsequently been amended by another user and then distributed by that other user Adapted Software If so that user may have additional license terms that applies to those amendments However FTDI has no liability in relation to those amendments 2 Product Page Document Feedback Copyright 2015 Future Technology Devices International Limited Application Note FTDI AN_371 FT90x WS2812 Example Chip Version 1 0 Document Reference No FT_001166 Clearance No FTDI 446 2 Theory 2 1 WS2812 LEDs WS2812 Serial LEDs use a One Wire protocol for communication which determines a bit based upon the pulse width of the symbol The WS2812 protocol uses three symbols a O bit a 1 bit and a Reset symbol used to latch in data These three symbols are described in Figure 1 Timing Diagram for WS2812 Symbols and Table 1 Timing for WS2812 Symbols 3 Product Page Document Feedback Copyright 2015 Future Technology Devices International Limited Application Note AN_371 FT90x WS2812 Example Chie Version 1 0 Document Reference No FT_001166 Clearance No FIDI 446 Figure 1 Timing Diagram for WS2812 Symbols frame Bescon win rvp mox uone toH O code High Voltage Time 200 350 500 t
12. ration of the 1 and 0 symbols lie within 1 25 usec allowing for a 150 nsec bit time for the 8 bit pattern For a 1 symbol the signal needs to be high for 650 to 950 nsec which corresponds to either 5 or 6 bit times For a 0 symbol the signal needs to be high for 200 to 500 nsec which corresponds to either 2 or 3 bit times Assuming that a 1 symbol uses 5 bit times and a 0 symbol uses 3 bit times this means that a 1 symbol will be high for 750 nsec and low for 450 nsec giving a mask of F8 Ob 1111 1000 anda 0 symbol will be high for 450 nsec and low for 750 nsec giving a mask of EO Ob 1110 0000 The function ws2812_ init in ws2812 gpio c shown in Table 2 Code Listing for Function ws2812_init sets up the GPIO pin as an output void ws2812_init void gpio_function WS2812_GPIO pad_func_ gpio_dir WS2812_GPIO pad_dir_output Table 2 Code Listing for Function ws2812_init The function ws2812_shiftout in ws2812_gpio c shown in Table 3 Code Listing for Function ws2812_shiftout 6 Product Page Document Feedback Copyright 2015 Future Technology Devices International Limited Application Note FTDI AN_371 FT90x WS2812 Example Chip Version 1 0 Document Reference No FT_001166 Clearance No FTDI 446 A implements shifting out a byte of data to a GPIO pin using the WS2812 protocol e The corresponding GPIO register and bitmask is determined
13. val amp mask asm _noop asm _noop asm _noop 7 Product Page Document Feedback Copyright 2015 Future Technology Devices International Limited Application Note FTDI AN_371 FT90x WS2812 Example Chip Version 1 0 Document Reference No FT_001166 Clearance No FTDI 446 P asm_noop if sym amp 0x04 gpioval else gpioval amp asm_noop asm_noop asm_noop if sym amp 0x02 gpioval else gpioval amp asm_noop asm_noop asm_noop asm_noop if sym amp 0x01 gpioval else snioval amp Table 3 Code Listing for Function ws2812_shiftout 8 Product Page Document Feedback Copyright 2015 Future Technology Devices International Limited Application Note FTDI AN_371 FT90x WS2812 Example Chip Version 1 0 Document Reference No FT_001166 Clearance No FTDI 446 A Using this function we can create the function ws2812_write in ws2812_gpio c shown in Table 4 Code Listing for Function ws2812_ write which sends out a RGB colour value on the GPIO pin void ws2812_ write uint8 t r uint8 t g uint8 t b ws2812_shiftout g ws2812_shiftout r ws2812_shiftout b Table 4 Code Listing for Function ws2812_write 3 2 HSV to RGB Colour Space Conversion Colour can be described in many different ways Typically colour is given as a level of Red Green and Blue RGB which is what the WS2812 LED uses to display a colour Howe
14. ver in order to simplify linearly fading through colour another colour space can be used This application uses the Hue Saturation and Value HSV colour space which allows for a more intuitive approach to colour manipulation e Hue defines what base colour to use e Saturation defines its colorfulness A high saturation gives a bright colour a low saturation gives grey e Value defines the level of brightness relative to full white Therefore by having a fixed saturation and value and cycling through the Hue a gradual fade of colour can be generated A conversion function is needed to convert from a HSV to a RGB colour space in order for HSV values to be used with WS2812 LEDs The function hsv2rgb in rgbhsv c shown in Table 5 Code Listing for Function hsv2rgb converts HSV values to RGB values This function uses fixed point math since the FT32 core does not support floating point void hsv2rgb uint8 t h uint8 t s uint8 t v uint8 t r uint8 t g uint8 t b Based on http stackoverflow com a 14733008 uint8 t region remainder p q t if s t V3 g V5 b y else region h 43 remainder h region 43 6 p v 255 s gt gt 8 q v 255 s remainder gt gt 8 gt gt 8 t v 255 s 255 remainder gt gt 8 gt gt 8 Switch region case 0 9 Product Page Document Feedback Copyright 2015 Future Technology Dev
Download Pdf Manuals
Related Search