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Lab 7 – Serial RF Communication. Start date: Week #10 Due date: Week #11. Serial Communications. 2 types of serial ports on the HC12 Serial communication interface (SCI) = asynchronous Serial Peripheral Interface (SPI) = synchronous - PowerPoint PPT Presentation
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Lab 7 – Serial RF Communication
Start date: Week #10Due date: Week #11
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Serial Communications
2 types of serial ports on the HC12 Serial communication interface (SCI)
= asynchronous Serial Peripheral Interface (SPI) =
synchronous
Know which one you want to use (RF has no clock signal pin)
2
SCI
Communication through port S SCI0 = PS0 (RxD), PS1 (TxD) SCI1 = PS2 (RxD), PS3 (TxD)
Can do parity (either even or odd)Supports 8 or 9 data bitsSC0 is in use – communication with terminal
3
Registers
SC0CR1/SC1CR1 Mode Parity
SC0CR2/SC1CR2 Transmit and receive enables Interrupt enables
SC0SR1/SC1SR1 Flags for complete and errors
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Registers
SC0DRH/L / SC1DRH/L Register to send/receive data through
SCI We will be using 8 data bits, so only
low is required
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Modes to use
Please set to use 1 start, 8 data, 1 stop No parity 9600 baud
Warning SC0 is already in use – this is what you use to communicate with the terminal
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RF module
The RF module sends and receives in 2 directions From board to RF, from RF to board The RxD and TxD lines are in reference to the
RF, ie send and receive over RF These will seem backwards from board
For RF modules with bent pins – just stick them upright into the boardWarning: sometimes the power light comes on when TxD or RxD is high – you still need to hook up the power or it will not work
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Sending Messages
Special Characters in use SOH – start of header
ASCII $01 STX – start of text
ASCII $02 ETX – end of text
ASCII $03 EOT – end of transmission
ASCII $04
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Sending Messages
Special Characters The base station prints the characters
as text because it is easier to read When you are printing you will see
them as special characters (^x)
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Message Passing
Base station sends out message to a groupThat group stores/prints the message and replies The base station stores/prints the message and repliesThe group stores/prints the message
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Message Format – Base Station
Base Station 1st send Message SOH GroupXX STX Message ETX EOT
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Message Format - groupXX
Group Reply STX Some message less than 20 chars ETX EOT
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Message Format – Base Station
Base Station Reply to group SOH GroupXX STX Some other message ETX EOT
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Summary of message passing
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General Notes / Hints
Please put a short delay between when you finish receiving and when you start sendingWe will wait for 1 second for a reply from each group Be aware that you may not receive anything for
that time it can be much longer than that before you
receive a message for your own group
Please do not send in other people’s time The RF modules cannot determine which is the
correct signal and the messages will get messed
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Testing
The base station will stay on for the whole week before the lab is due – front row Sending and receiving messages will be printed
on the screen
The TA’s will transmit as the last group (group 7) This is to check that the BS is actually
transmitting If you don’t see the TA group message, the
base station may not actually be transmitting We will try to check on it, but if there is a
problem, please email us
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Academic Misconduct
Reports and demos are submitted as a group, but it is a SINGLE group effortYou may talk with other groups but sharing code or reports is NOT ALLOWEDCopying code/reports from previous years is also NOT ALLOWEDIf we find copying we are REQUIRED to report it
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