7/16/2015EECS150 Spring Wireless Transceiver EECS150 Spring 2008 Shah Bawany

7/16/2015EECS150 Spring This Lab Lecture… Timeline Checkpoint 3 Overview Checkpoint 2.5 Overview

7/16/2015EECS150 Spring Timeline Checkpoint 1 Was due this week If you didn’t finish, turn it in as soon as you do for partial credit Checkpoint 2 Design Reviews were this week Code due after break Very easy checkpoint, but we are only postponing the due date so you can make thoughtful designs for checkpoint 3 (we will grade them much more harshly) and so that you can catch up if you’ve fallen behind (by working all break

7/16/2015EECS150 Spring Timeline (2) Checkpoint 2.5: 4-Port Arbiter, Frame Subsampling, Complete UI An early start on Checkpoint 4 for those looking to work ahead. If you make a design for the CP3 design review AND get checked off for it with CP3, you will get 5% extra credit on CP3. Specs will be up this weekend Checkpoint 3: Wireless Transceiver Specs up now, Design Reviews next week Due the week after CP2 (the 2 nd week after break) The time given for this checkpoint is justified by its difficulty

7/16/2015EECS150 Spring Timeline (3) Checkpoint 3 (continued) Some additional tools will be released this weekend or early next week Packet sniffer - For detecting what’s being transmitted on a wireless channel) TA solution - To test transmit / receive independently Checkpoint 4: Integration and Compression Specs will hopefully be up before break Lab lecture will be the week you return from break Design reviews will be the same week CP3 is due Final project (CP4 + extra credit) due 2 weeks after CP4 design reviews

7/16/2015EECS150 Spring Transceiver Overview (1) 3 rd party chip mounted on expansion board. Uses a PCB antenna. Take a look! IEEE standard support. Transmits on unlicensed 2.4 GHz spectrum. 16 communication channels. Overlaps with Wi-Fi. 250 kbps maximum data rate. In use in the project, we can achieve 16KBps Configure, send, receive, and issue commands to chip over SPI to CC2420 registers.

7/16/2015EECS150 Spring Transceiver Overview (2) 33 configuration registers. We change 3 of them. 15 command strobe registers. We issue 6 of them. These change the state of the CC2420 internal FSM. 128-byte RX FIFO & 128-byte TX FIFO Accessed via 2 additional registers. Also accessible as RAM (i.e. by addressing). Only for debugging! Don’t do this unless you’re a masochist

7/16/2015EECS150 Spring Transceiver Overview (3) You will need to read the data sheet to learn more about how the CC2420 works in more detail than what we can fit in the Spec. MDPU Status Registers (more info.) Commands (more info.) Internal state machine (very helpful!!)

7/16/2015EECS150 Spring CC2420 Inputs & Outputs FPGA VREG_EN RF_RESET_ Single bit status signals. High level transceiver operation information. Initialization signals. Drive signals once and forget about it. SPI interface. Interface to rest of chip via CC2420 registers. Send, receive, configuration, detailed status.

7/16/2015EECS150 Spring Single Bit Status Indicators FIFO – Goes high when there’s received data in RX FIFO. FIFOP – Goes high when # bytes received exceeds set threshold. CCA – Indicates that the transmission medium (air) is clear. Only valid after 8 symbol periods in RX mode. SFD – Goes high after SFD is transmitted & low after packet completely sent.

7/16/2015EECS150 Spring SPI Interface Serial interface with 4 wires: SClk – Clock signal you generate. CS_ – Active-low chip select. SI – Output to the CC2420. SO – Input from the CC2420. Interface to the chip! Initialization, configuration, TX, RX, detailed status. Luckily for you, it’s provided as a black box.

7/16/2015EECS150 Spring CC2420-specific SPI (1): First Byte First byte always has above format. Bit 7 – Set to 0 for register access. Bit 6 – Read/write control. Bits 5:0 – Address of register. P. 60 of datasheet. Followed by data specific to register being accessed. Sent First  Bit Position  Sent Later 765:0 1 = RAM access (not used) 0 = register access 1 = read 0 = write Address of register. Refer to p. 60 of the datasheet.

7/16/2015EECS150 Spring CC2420-specific SPI (2): Writing to Configuration Reg. First byte followed by 2 bytes of configuration data. Data on SO invalid here. Transceiver replies when first byte is sent out with status byte. True for all SPI accesses. Not necessary to inspect, but can be helpful for debugging! Sent First  Byte Number  Sent Later Sent on SI address byte, described above16 bits of data to be written to register Received on SO status byte16’bX

7/16/2015EECS150 Spring CC2420-specific SPI (3): Issuing Command Strobes One byte only. Nothing follows. Address sent indicates the command strobe being issued. Note that 0x00 is NO OP. This is useful for explicitly retrieving status byte. Byte Number 1 Sent on SI address byte, described above Received on SO status byte

7/16/2015EECS150 Spring CC2420-specific SPI (4): Saving to TX FIFO After first byte, send n bytes of data to transmit over wireless. SPI session only ends when CS_ is pulled high. CC2420 replies with a new status byte with each byte that’s saved to FIFO. Sent First  Byte Number  Sent Later 12 to n Sent on SI address byte, described abovedata bytes to be transmitted Received on SO status byte

7/16/2015EECS150 Spring CC2420-specific SPI (5): Receive from RX FIFO After first byte, send a n bytes of “don’t care” in order to receive data. During first byte, CC2420 replies with status. Subsequent bytes are data saved in FIFO. Must be careful not to request data from empty FIFO! SPI session only ends when CS_ is pulled high. Reading from a configuration register is the same. Received First  Byte Number  Received Later 12 to n Sent on SI address byte, described above8’bX Received on SO status bytedata from the RX FIFO

7/16/2015EECS150 Spring Configuration Registers RegisterAddressBit(s) of Interest Purpose MDMCTRL00x1111Turn off automatic address recognition. You must set bit 11 to 1’b0. FSCTRL0x189:0Channel changing. IOCFG00x1C6:0Changes the threshold of number of bytes in RX FIFO before FIFOP goes high. Defaults to 64. You may want to change this value.

7/16/2015EECS150 Spring Command Strobe Registers RegisterAddressPurpose SNOP0x00No operation. SXOSCON0x01Turns on the crystal oscillator and will be used as part of the initialization process. SRXON0x03Moves the CC2420 into the receive state and will be used as part of the initialization and channel changing process. STXON0x04Instructs the CC2420 to transmit the data contained in the TX FIFO. SRFOFF0x06Turns off RX/TX and frequency synthesizer and will be used as part of channel changing. SFLUSHRX0x08Flushes the RX FIFO. This command will be used a lot!

7/16/2015EECS150 Spring TX/RX FIFO Registers RegisterAddressPurpose TXFIFO0x3EFor saving bytes to transmit into the TX FIFO. You must not write data to the FIFO while a transmission is in progress. RXFIFO0x3FFor retrieving bytes from the RX FIFO.

7/16/2015EECS150 Spring Initialization

7/16/2015EECS150 Spring Transmit

7/16/2015EECS150 Spring Transmit(2) CC2420 needs 12 symbol periods to move into RX_SFD_SEARCH state after transmit done or SRXON. 1 symbol period = 16 us. Without enforcing wait, aggressive user of your Transceiver module will cause CC2420 to never receive data from air.

7/16/2015EECS150 Spring CCA If you don’t follow CCA we will dock MAJOR points If CCA isn’t high, you must wait a RANDOM AMOUNT OF TIME CCA may also not go high if you have buffer overflow. FIFOP & !FIFO

7/16/2015EECS150 Spring Receive (1)

7/16/2015EECS150 Spring Receive (2) You must be able to receive while the random CCA wait time is expiring! Packets are only received after CC2420 has spent 12 symbol periods in receive mode. There must be wait time between transmissions. Allows the transceiver to look for and receive data.

7/16/2015EECS150 Spring Receive(3) Refers to 2 things: 1. CC2420 is constantly receiving and saving data into RX FIFO as long as it’s not transmitting. Look at CC2420 internal FSM on p You have to “receive” data from RX FIFO, filter it, then save wanted data into SPIFifo.

7/16/2015EECS150 Spring Design Structure (1) Transceiver – Highest level block. 32-bit input/output, channel changing, addressing. SPI Abstraction – Takes care of details of CC2420 SPI interface. Arbitrates between TX/RX. SPI (provided) – Handles details of interface timing.

7/16/2015EECS150 Spring Design Structure (2) High level FSM behavior Upon receiving a request to transmit, load TX FIFO, but wait till CCA clear to send If CCA not clear, check if RX FIFO has something to recieve If data in RX FIFO, read data then check CCA again but do not assert ready until you have transmitted the last piece of data If CCA is clear, transmit return to ready state

7/16/2015EECS150 Spring Design Structure (3) High level FSM behavior (continued) Hint: One implementation of the overall FSM includes a state for initialization, a ready state, 2 CCA wait states, 2 TX states (load/send) and an RX state. Each of these states engages one of the FSMs presented on the previous slides.

7/16/2015EECS150 Spring Packet Format MPDU PreambleSFDLengthSourceDest.PayloadFrame Check Sequence (CRC) 4 bytes1 byte 32 bytes2 bytes 0x000x7A ??? Design Review Question! sender’s addr. recipient’s addr. or 0xFF For broadcast data  On transmit, 0x00.  On receive, bit 7 of the 2 nd byte is 1 when CRC ok, 0 otherwise. On transmit, only fill TX FIFO starting with length byte. Preamble & SFD automatically appended. Transmit all zeros for CRC. CC2420 will replace.

7/16/2015EECS150 Spring Channel & Addresses There are 16 channels. Your group will be assigned a channel. You must be able to change channels without reset! DO NOT USE ANOTHER CHANNEL BESIDES YOUR OWN This is a big class and we need to be able to partition the signal space! Address are 8-bits wide  256 addresses. Zero is unused. 0xFF is reserved for broadcast.

7/16/2015EECS150 Spring Interference & Debugging Roughly 2-3 groups per channel. Each group in a particular lab has distinct channel. Can also pick up data on neighboring channel. Very first goal is robust channel changing during initialization. Can pick up packets sometimes. Your module must recover gracefully. Your project interferes with Wi-Fi & vice versa.

7/16/2015EECS150 Spring Handshaking: InRequest/Invalid SPI uses a variation of this. You may want to use this internally.

7/16/2015EECS150 Spring Handshaking: Ready/Start Transceiver uses this interface for input & output.

7/16/2015EECS150 Spring Design Structure (4) When you receive a START signal, do not assert READY until you have issued the command to actually transmit the value you have loaded into the TX FIFO Upon receiving a START signal, store the input into the TX FIFO, but wait for CCA to be clear before transmitting

7/16/2015EECS150 Spring Debugging Tools Chipscope! We will be releasing some debugging utilities. Packet sniffer. Packet counter (The TA Solution does this)

7/16/2015EECS150 Spring Get Started! READ THE DATASHEET Obey our CCA rules

7/16/2015EECS150 Spring Danger! Don’t become complacent because you’ve *been* finishing checkpoints early Expect each checkpoint to be at least twice as difficult as the last. 1>>2>>>>3>>>>>>>>4! Get started early and get ahead.

7/16/2015EECS150 Spring Checkpoint 2.5 Complete UI:

7/16/2015EECS150 Spring Checkpoint 2.5 Four Port Arbiter: SDRAM Controller SDRAM Arbiter VD Proc.VE Proc. SubsamplerPIP Proc. Wireless Rec. Proc. Wireless Send Proc. Display Camera CP4 DCT/ Huffman CP3 Wireless Channel Wireless Out Wireless In

Checkpoint 2.5 Check the website regularly for full the updated full spec. It makes sense to start this as soon as you finish CP3 since you will have to do it anyway Extra credit incentivizes it more Any questions?