AVR459: SB200 Hardware User's Guide
Contents
1. 13 AMEL AIMEL 14 6 2 Write command On write commands the host can start to send data to SB201 after it has received the replied command byte After SB201 has received the whole message it will execute the command if it was understood and the PEC was correct It will send an ACK back to the host after it has finished executing it If the command was supported but the PEC wrong a NACK is sent back On all other errors nothing is sent back ACK is OxFF and NACK is 0x00 Figure 14 2 A read word command From host Command From slave Gana Data byte Data byte PEC low high Figure 14 3 A write word command Data byte Data byte From host Command ee high PEC From slave OET ACK NACK Figure 14 4 A read block command From host Command Prom siave Command Data 0 31 PEC Figure 14 5 A write block command From host Command Data 0 31 PEC From slave STET ACK NACK 14 AVR459 8132A AVR 10 08 14 6 3 Errors 8132A AVR 10 08 AVR459 At 4800 baud there is only 208 clock cycles for SB201 between each bit This means that to ensure error free communication all the time all other interrupts would have to be less than 104 cycles including the prologue of the timer interrupt Thi2. AVR459 SB200 Hardware User s Guide AIMEL ae O Features e Full evaluation of Atmel smart battery reference design e Socket for SB20x smart battery reference designs Development platform for AVR based smart batteries e Communication gateway between PC and smart battery Single Wire UART for single and dual cell batteries TWI SMBus interface for larger batteries e Battery Charger Charge with up to 19V and 2A n Auto limitation of charging voltage and current Application Note Auto termination of charging when charging period expires e Adjustable Constant Current Load for battery discharging Sink up to 4A continuous current Auto shut down if too hot 8 bit AVR Microcontrollers 1 Introduction The SB200 is a development platform for SB20x smart battery reference designs which offers an easy way to start evaluation and hence development of smart battery applications using Atmel AVR microcontrollers The SB200 is not in itself a reference design but is intended to be used with e g SB201 1 which is a reference design that demonstrates implementation of a single cell smart battery Li lon 16340 CR123A battery cells can be inserted in the SB200 battery sockets and a SB20x is inserted in the dedicated daughter board socket This forms a battery pack with a given number of cells safety protection and full battery capacity monitoring capabilities Alternately other cell types can be soldered in
3. 3 Communication AVR459 When setting maximum current and voltage the charging time in minutes is also set This can be up to 255 minutes and the Charger will stop when the time is reached The HWB button on SB200 starts a charge cycle with a duration of 1 minute or until you press it again The charge voltage is set depending on which SB20x that is connected This will also power up the SB20x if it was off The voltage current and timeout will be sent to the PC The ADC on tiny861 has an external reference of 2 5V and with 10 bit ADC this give a resolution of 2 44mV The voltage input to the ADC is scaled down 8x so max voltage possible to measure is 19 98V and resolution is 19 5mV The current input uses the differential input with 20x gain over a shunt resistor of 0 5Q This is also scaled down 8x thus giving a resolution of 1 95mA so max current possible to measure is 2A The PWM output to the buck converter has 512 values which means a resolution of Input Voltage divided by 512 e g at 10V input the resolution will be approximately 19 5mV Note that the battery cell voltage reported in the SB200 PC application may vary during charging This is because the Charger is continually adjusting the voltage to match the voltage and current limits set The Charger has a simple communication interface on the SPI bus It understands two commands One command is SetCharging and it configures maximum current maximum voltage an
4. 7V The supply voltage need not be 20V but needs to be a few volts higher than the maximum voltage of the battery stack on the board The Charger and the opamp s in the Constant Current Load need that to function properly If a two cell smart battery application is being developed it is therefore sufficient to connect e g 10V A higher voltage will only generate unnecessary heat in the board supply regulator which is used to generate 5V for the USB1287 tiny861 and the DAC The Charger on the SB200 can deliver 0 20 volts and 0 2 ampere using a constant current constant voltage charging scheme It is configured by setting maximum voltage maximum current and timeout The Charger will make sure that no limit is exceeded and will try to make sure one of them is reached A fast PWM output on the Charger is connected via a buck converter to the battery By changing the duty cycle on the PWM the voltage to the battery can be adjusted To be able to measure voltage and current two ADC pins is connected on both sides of a shunt resistor just before the battery The Charger continuously measures the voltage and current and adjusts the PWM output accordingly The PWM is adjusted one step at a time and this will make it take approximately seven tenths of a second to go from minimum to maximum output If either maximum current maximum voltage or timeout is set to zero charging will stop immediately 8132A AVR 10 08 7 2 Resolution 7
5. C a o onw O Notes 1 Test point reserved for future use 10 Programming the USB1287 or the tiny861 Reprogramming of the AT90USB1287 USB gateway and board controller and the ATtiny861 that controls the Charger is possible and may be required to use the latest version of the firmware It is recommended to always upgrade to the latest version of the firmware found on www atmel com to ensure that the firmware match this documentation and operates accordingly The firmware source code running in these devices are available but only as an extra service These devices are part of the AMEL 8132A AVR 10 08 AMEL development platform not part of a reference design Therefore the source code for these devices are provided as is and with limited support The product supported fully is the source code for the reference designs such as the SB201 One case where update of the USB1287 firmware can be relevant is if a different communication protocol is desired to be used between the smart battery and the host During the development it can be desired to use the USB1287 as a gateway to communicate with the smart battery via this interface protocol Changes and extensions to the communication interface protocol are left to the users to implement To program the tiny861 the USB cable must be disconnected and the USB1287 will release the SPIl lines which are used for inter communication Figure 10 1 Programming interfaces for USB128
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7. Simple checksum byte the sum of previous bytes e Carriage return character The package is minimum 7 bytes and maximum 262 bytes in size DATA is transmitted only if NBYTES is nonzero Example Send 2 bytes from PC to Electronic Load SYNC ADDRESS SENDER COMMAND NBYTES DATA CS ole ple 2 wma cas gt 14 1 1 Source and destination ADDRESS Address ASCII Address hex HW Module a 14 2 Global COMMAND The commands for the different hardware modules are covered in the sections below Commands can be uses in both read and write mode if a command code ASCII is sent as upper case it is a WRITE and if in lower case it is a READ Each module has its own unique commands commands not shared for different hardware modules In the following explanations the COMMAND is marked yellow 14 3 COMMAND to Constant Current Load The Constant Current Load only supports write commands It is implemented with a 14 bit DAC and the Board Controller will process the requested current level to achieving the correct current level for the Constant Current Load The Board Controller will also monitor the PCB temperature and shut off the Constant Current Load if the PCB temperature is higher than 125 C Example Set Constant Current Load to 2450mA SYNC ADDRESS SENDER COMMAND NBYTES DATA cS CR v e p e p m gt 10 AVR459 8132A AVR 10 08 AVR459 14 4 COMMAND to from Charger 14 4 1 SetCharge
8. any technical or legal requirements that are applicable to finished products including without limitation directives regarding electromagnetic compatibility recycling WEEE FCC CE or UL except as may be otherwise noted on the board kit Atmel supplied this board kit AS IS without any warranties with all faults at the buyer s and further users sole risk The user assumes all responsibility and liability for proper and safe handling of the goods Further the user indemnifies Atmel from all claims arising from the handling or use of the goods Due to the open construction of the product it is the users responsibility to take any and all appropriate precautions with regard to electrostatic discharge and any other technical or legal concerns EXCEPT TO THE EXTENT OF THE INDEMNITY SET FORTH ABOVE NEITHER USER NOR ATMEL SHALL BE LIABLE TO EACH OTHER FOR ANY INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES No license is granted under any patent right or other intellectual property right of Atmel covering or relating to any machine process or combination in which such Atmel products or services might be or are used Mailing Address Atmel Corporation 2325 Orchard Parkway San Jose CA 95131 Copyright 2008 Atmel Corporation 8132A AVR 10 08 Headquarters Atmel Corporation 2325 Orchard Parkway San Jose CA 95131 USA Tel 1 408 441 0311 Fax 1 408 487 2600 International Atmel Asia Room 1219
9. 14 1 Bits controlling RGB colors moo ooo po we ooo p 14 5 2 Read the SB20x Hardware ID AVR459 When the Board controller has identified the hardware ID of the SB20x daughter card refer to AVR455 SB201 Hardware User s Guide the PC software can query that ID using the commands below Read_SB20x_HWid SYNC ADDRESS SENDER COMMAND NBYTES es CR wo mwm p h p wb Response Send_SB20x_HWid sync ADDRESS SENDER COMMAND NBYTES DATA cs or v e pu h a ew 14 5 3 Set the Battery Select LED The PC software can query SB20x_HWid and then send a package to give a visual feedback to the user about where to place the red jumper After reset of USB1287 this is done automatically by USB1287 Batteryx_Led i e SET Cell2 Led on SYNC ADDRESS SENDER COMMAND NEYTES DATA cS GR vo pm e moo po fe cae gt Led Value 4 3 2 1 Table 14 2 Byte controlling the of Cells Leds of Cells DATA 8132A AVR 10 08 AVR459 14 5 4 Read the SB200 PCB Temperature The NTC placed close to the Constant Current Load can be read Response is a temperature between 40 C to 125 C Read_Temperature v m P e Response Send_Temperature sync ADDRESS SENDER COMMAND NBYTES DATA cS on v p m k p wm 14 6 Communication protocol between the USB1287 gateway and SB201 SB204 14 6 1 Read commands 8132A AVR 10 08 The communication between the S
10. 7 and tiny861 El E EENE d lr m unmmnul fpu Eg E EH in TETIT ae il pe Eo nr e e USB1287 JTAG z it it a oo n F annant w amp p a 7 on LULL ee eee ee Pita ten o E T Sae2 gu a 15 im z Se gt Tiny861 SPI ISP rrea ueu s nn mE E E TEET E EE m n e E m E m mm n x m m pmm r ae ilill g ha 11 Buttons Next to the USB1287 two buttons are present Reset will reset the USB1287 device and the Constant Current Load HWB will either enable the Charger for a short time to start the smart battery device or it will stop the Charger next time the button is pressed SB201 1 4200mV 100mA SB201 2 8400mV 100mA 12 Status LED An RGB LED is located between the buttons This indicates the status of the USB1287 When the LED is red the USB1287 is transmitting and when it is green the USB1287 is receiving As transmission is so fast that the human eye cannot distinguish the individual colors the LED would appear yellow during transfers 8 AVR459 8132A AVR 10 08 AVR459 13 DB101 support for portable demonstration A DB101 can be placed on the female pin header This is an alternative to using a PC as host The DB101 would typically only be used for demonstration where standalone battery powered operation is desired Atmel does not provide firmware for this 13 1 Battery cells provided with SB200 Though the capacity of the cells is specified to 880m
11. Ah they are actually closer to 7OOmAh The cells have built in protection which affects the characteristic of the battery It can be an advantage to use unprotected cells if a more correct behavior is desired However it is recommended to use protected cells until the implementation is verified to not allow overstress of the connected cells 14 Communication Gateway An AT90USB1287 AVR microcontroller acts as both communication gateway and board controller It passes messages from its USB interface to other units on the SB200 The communication links on the SB200 is shown on Figure 14 1 The figure also shows reference designs SB204 and SB202 which are not available upon release of the SB200 Figure 14 1 Communication links on and off the SB200 A SH1 protocol SBS on half duplex UART lo 1O SBS on SMBus 19 SH1 protocol write commands only Word data write commands only Host Host PC DB101 Half Duplex UART SB200 Gateway SPI SPI 5 USB1287 SMBus Smart Electronic 14 1 Communication protocol between the Host PC and the USB1287 gateway 8132A AVR 10 08 The SH1 protocol is built to be tested invoked from a terminal that s the reason for all the ASCII characters The package uses a AMEL GH AIMEL E e Fixed character as preamble to indicate start of package e Destination address byte e Source address byte e Command byte e Size byte e Data payload e
12. B200 and SB201 SB204 is based on a half duplex UART here referred to as Asynchronous smart battery bus ASBBus The SBS specification uses the SMbus protocol but since SB201 uses software UART some changes have been made to improve reliability Addressing has also been removed SB201 supports the four different types of messages used by SBS e Read word e Write word e Read block e Write block A word command always has two bytes of data and a block command always 32 bytes which is different from the SBS block commands that has variable length The host sends a command where the MSB determines if it s a write or read O means write and 1 means read This allows for 128 different commands that both support read and write From the command itself it is not possible to determine if it is a word or block command both sides have to agree what all commands are SB201 immediately sends back the command this allows the host to detect if SB201 received the command correctly What happens after that depends on the type of message used by that command A Packet Error checking Code PEC is appended to all data to be able to detect errors The PEC is a CRC8 with polynomial 0x8D CRC8 CCITT calculated from the command and all data bytes On read commands SB201 starts to send data after it has sent back the command The PEC is also appended However if the command wasn t supported nothing is sent back except for the command byte
13. F ATMEL HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES Atmel makes no representations or warranties with respect to the accuracy or completeness of the contents of this document and reserves the right to make changes to specifications and product descriptions at any time without notice Atmel does not make any commitment to update the information contained herein Unless specifically provided otherwise Atmel products are not suitable for and shall not be used in automotive applications Atmel s products are not intended authorized or warranted for use as components in applications intended to support or sustain life 2008 Atmel Corporation All rights reserved Atmel logo and combinations thereof AVR and others are the registered trademarks or trademarks of Atmel Corporation or its subsidiaries Other terms and product names may be trademarks of others 8132A AVR 10 08
14. ards e Battery cell socket 5 s a lt Connector for DB101 e 4 Details of the SB200 blocks The following sections describe the SB200 blocks on a functional level Electrical schematics a Bill of Materials and CAD gerber files are available as separate files which can be downloaded from the Atmel web site hitp www atmel com sb200 The source code for the SB200 firmware is available from the Atmel web site as well but is provided as is No support is provided on this part of the code as it is made as a development tool for smart battery application only SB200 firmware is based on demo application for AT9OUSBKEY The supported code is therefore only the source code for the SB20x smart battery reference designs 8132A AVR 10 08 AMEL 5 Insertion of battery cells and placement of the corresponding jumper 6 Supply voltage 7 Charger 7 1 How it works 4 AVR459 Insert only the number of battery cells that are intended to be used with the SB20x in the SB20x daughter board socket Further make sure to place the jumper that selects the number of cells correct otherwise one of the battery cells will be shorted sep aion o e 2 femsa PSS e fsmew SSS Recommended order s racemos 6 _ Pace Red Jumperconect orvosi 7 renses SSS fe _ PressHweuton ore mine crargeissana SB200 can be supplied with up to 20V through the DC jack The DC jack has positive center Minimum supply voltage is
15. ately 125 C by turning off the load if the temperature rises above this point Figure 2 1 Constant Current Load hot heat sink The SB200 is developed to ease development of Smart Battery applications It offers a communication gateway between the SB20x reference designs which uses half duplex UART or SMBus to USB It can charge the batteries connected or inserted in the board and act as a load to investigate behavior during discharging of the battery The SB200 comes with a PC software that controls the various features of the kit An introduction to this software is found in application note AVR491 quick start guide for SB200 Both the executable and the source code for the PC software are available from the Atmel web site and can be installed into AVR Studio An overview of the hardware is seen in Figure 3 1 8132A AVR 10 08 AVR459 Figure 3 1 Placement of hardware modules on SB200 areas within silkscreen rectangles shape E z Constant current load p a Test point N T Connection point for USB Gateway board external battery cells p gt controller also available at ee other cell sockets e EE ee se T LEINE ee E E ee o en e p E E Board supply m max 20V input a _ s Zj a on e aO T Charger amp EE n an Lis OLTE memes Jumper for way TI pack cell configuration m E Test points e Connector for SB20x a reference design o daughter bo
16. d and it can AMEL AIMEL Gy therefore be used to test and characterize battery cells and application The load can be calibrated to get better accuracy and linearity by rewriting the firmware for SB200 8 1 Short circuit load condition The load is implemented as an integrating circuit This means that it can be used to simulate high out rush currents if the load is enabled but no current source is available it will saturate and open fully max load When a voltage current source is enabled the load will for a short moment draw maximum current and can be seen as a short circuit load As soon as the current starts flowing the load will start to adjust the current to reach the target level This can cause problems if one is not aware of this since the smart battery AVR MCU will be detect this as a high current over current short circuit situation However this characteristic of the load can be used to test an implementation of a smart battery as it can be used intentionally to trigger a high out rush current situation and validate correct behavior 9 Test and connection points 9 1 External connection 9 2 External battery cells 9 3 Signal line test points 6 AVR459 The SB200 offer a variety of test and connection points some for easy access to relevant signals with scope probes and others to make it possible to connect external units On each side of the heat sink at the Constant Current Load connection point
17. d timeout The other command is ChargerRead This command to the Charger reads the voltage and current seen from the ATtiny861 Please refer to section 14 4 for more information about the communication If it receives any other command doesn t get all parameters or notices a checksum error it will just discard the message The implementation is based on the BC100 reference design and application note AVR458 Please refer to this application note for more information about charging Li lon batteries 8 Constant Current Load 8132A AVR 10 08 The constant current is implemented with a 14 bit DAC differential amplifiers and two MOSFET transistors operated in their linear mode The reference is 5V step size is approximately 305uV Shunt resistor is two of 0 5Q in parallel Resolution is 1 22mA and max current is 20A The load can draw high currents for a short time and is mainly limited by thermal overstress The current drawn by the load is controlled from the PC software If the current is kept below 2A for single cell and 1A dual cells applications the load should not overheat the higher the voltage of the battery stack the lower should the current be The USB1287 monitors the temperature of the load and will shut it down if it reaches 125 C to avoid damage to the MOSFET s The load has fairly good accuracy at higher currents while it may be somewhat inaccurate at lower currents The constant current stability is very goo
18. r The command to the Charger sets the maximum limits for charging voltage and current and the charging time The Charger will not exceed either of those but will adjust the voltage and current levels to get as close to the limits as possible SetCharger i e 8400mV 450mA 10 minutes o PSS mm mm charminutes Cale gt 14 4 2 ChargingInfo The response from the Charger is sent when the HWB button is pressed This will update the PC software CharginglInfo i e 0000mV 100mA 1 minute SYNC ADDRESS SENDER COMMAND NEYTES DATA DATA oara os Jon upc fs itv intma charminutos Calo gt 14 4 3 ChargerRead This command to the Charger reads the voltage and current seen from the ATtiny861 ChargerRead rsync ADDRESS SENDER COMMAND NAYTES cs Jon vo p p R p Jap 14 4 4 ChargerReport The report from the Charger is sent when the PC has asked This will update the PC software ChargerReport i e 8385mV 607mA SYNC ADDRESS SENDER COMMAND Nevres para DATA os Jon w p e dint em e 14 5 List of COMMAND to from Board controller 14 5 1 Set the RGB LED Command to set the color of the RGB LED between the two switches at USB1287 11 AMEL 8132A AVR 10 08 AIMEL Leds_set_val i e SET RED Led on SYNC ADDRESS SENDER COMMAND NBYTES DATA CS ee a S Where the bits in DATA that enabled the individual colors in the RGB LED are listed in table Table
19. s are available These can be used to measure the battery stack voltage or an external charger can be connected here The connection points are designed to match a 4mm power connector such as Farnell no 1101128 1101127 This makes it also easy to connect an external load if the on board load is not sufficient It also allows for the on board load to be used towards an external target for testing purposes If it is desired to connect battery cells to the SB200 that does not fit in the sockets these can be placed on an external board and connected to the SB200 test connection points at each of the battery cell sockets see Figure 3 1 These connections points can also be used to connect an external power supply instead of batteries This can be used to more easily and safely test how the smart battery implementation reacts to extreme voltage current conditions If working with cells that fit in the sockets these test connection points can be used to measure the voltage over the battery cells All signals available on the SB20x edge connector are available as test points These are located next to the SB20x daughter board connector see Figure 3 1 2 54mm pin headers can be mounted to make it easier to hook a scope probe to these test points 8132A AVR 10 08 AVR459 Table 9 1 Signals on the test points next to the SB20x daughter board connector Test point designator Signal Description e a e a e a e T e a C a K T
20. s is not always true for the interrupt service routines used by SB201 However since those interrupts CCADC amp VADC conversion complete only runs once per second and since the blocking interrupts has to occur just a few cycles before the timer interrupt a retransmission of the broken communication is sufficient and adequate to solve this The errors the host can detect include e Wrong command returned by SB201 e Frame error on data sent from SB201 e PEC incorrect on data sent from SB201 e B201 does not respond within reasonable time min 50ms e SB201 sends a NACK to indicate an error occurred On all those errors the host should send a break arbitration lock and retransmit A break arbitration lock is a minimum of 18 normal bit periods of low on the communication line This resets the communication on SB201 and makes it ready to receive a new transmission A break can be sent as soon as the error is detected If the same command fails many times in a row that command is probably not supported by SB201 or something serious is wrong It might be that the frequency of the clock on the host or SB201 has changed too much or maybe that SB201 have shut itself down 15 AMEL 15 EVALUATION BOARD KIT IMPORTANT NOTICE AVR459 This evaluation board kit is intended for use for FURTHER ENGINEERING DEVELOPMENT DEMONSTRATION OR EVALUATION PURPOSES ONLY It is not a finished product and may not yet comply with some or
21. to the SB200 To simulate the use of the battery pack the SB200 features a Charger that can charge the battery pack and a Constant Current Load that can simulate an application that draws power from the battery pack Figure 1 1 SB200 with two batteries and SB201 2 inserted Rev 8132A AVR 10 08 AMEL 2 Safety precautions when using Li lon batteries 2 1 Warning HOT 3 Functional overview 2 AVR459 The batteries provided with the SB200 have built in protection which might cause strange effects to occur if the battery is exposed to overstress situations such as over charging The built in protection does affect the battery characteristics especially in terms of resistance but will ensure that even incorrect use and bugs in a smart battery application under development does not pose a safety hazard Nevertheless if battery cells heat up are physically damaged or shows other signs that can cause or be a consequence of malfunction the battery cell should be discarded into a safe deposit If other batteries without protection are used please observe the safety guidelines following the batteries Li lon and Polymer batteries amp packs may explode and cause fire if misused or defective Be aware that the heat sinks of the Constant Current Load can get very hot The shunt resistors 0 5Q at the load and from the charger will also get very hot Do not touch them The SB200 will limit the temperature to approxim
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