1. EEE527 Embedded Systems Lecture 9: Chapter 9: UARTs (version 2 – 25/11/13 changed slides 11-17, added new at end) Ian McCrumRoom 5B18, Tel: 90 366364 voice mail on 6 th ring Email: IJ.McCrum@Ulster.ac.uk Web site: http://www.eej.ulst.ac.ukIJ.McCrum@Ulster.ac.ukhttp://www.eej.ulst.ac.uk "Adapted from the text “Programming 32-bit Microcontrollers in C – Exploring the PIC32, © 2008.” Lucio di Jasio www.eej.ulster.ac.uk/~ian/modules/EEE527/files

2. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Simplified UART block diagram figure 19-1 (DS61143)

3. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Baud Rate setting In our case this translates to the following expression: U2BREG = (25,000,000 / 4 / 115,200) -1 = 53.25 To decide how to best round out the result, use the reverse formula to calculate the actual baud-rate and determine the percentage error: Error = ((Fpb / 4 / (U2BREG + 1)) – baud rate) / baud rate % With a value of 53 -> 115,740 Baud with an error of just 0.47%, With a value of 54 -> 113,636 baud, 1.82% error, Both are within the acceptable tolerance range for a standard RS232 port (+/- 2%). We can therefore define the constant BRATE as: #define BRATE 53 // 115,200 Bd (BREGH=1)

4. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Use Excel to Calculate values SYS_CLKPB divisorPBCLKBaudrateUxBRG Actual BaudrateError Actual BaudrateError =PBCLK/(4*baud) -1'Round Downfor Rounded down Round upfor Rounded up =PBCLK/(4*(UxBRG+1))' Number FormulaNumberFormula e.g C8=A8/B8 E8=C8/(4*D8) - 1=roundown(E8,0)G8=C8/((4*(F8+1))(G8-D8)/D8=roundup(E8,0)J8=C8/(4*(I8+1))(G8-D8)/D8 5000000022500000011520053.2534722253115740.74070.47%54113636.3636-1.82% 5000000022500000038400161.760416716138580.246910.47%16238343.55828-0.61% 5000000022500000019200324.520833332419230.769230.16%32519171.77914-0.31% 500000002250000009600650.04166676509600.6144390.01%6519585.889571-0.15% 5000000022500000012005207.33333352071200.0768050.01%52081199.84642-0.02% See the File EEE527_PIC32MX_BAUD_RATE_GENERATOR.xlsx

5. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum UxMODE register register 18-1 (DS61168E)

6. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Important BITs of UxMODE ON (bit 15) 1 is enabled, UARTx pins controlled by UEN and UTXEN SIDL (bit 13) only relevant in idle mode IREN (bit 12) 0 = IrDA is disabled RTSMD (bit 11) 1 = /UxRTS is in Simplex mode UEN (bits 9-8) 00 = Use UxTX/RX, /UxCTS,/UxRTS/BCLK just used by PORTx WAKE (bit 7) only relevant in sleep mode LPBACK (bit 6) 0 = loopback disabled ABAUD(bit 5 ) 0 = Auto-Baud rate detection is disabled or completed. RXINV (bit 4) 0 = UxRX idle state is a ‘1’ ( sent in RS232 as -12V!) BRGH (bit 3) 1 = High-speed mode – 4x baud clock enabled. {0= x16} PDSEL (bits2-1) 00 = 8 bit data, no parity {01=8E, 10=8O (odd), 11=9N } STSEL (bit 0) 0 = 1 stop bit {1 = 2 stop bits} - - - - - - - - - - - - - - - - 1ux0 1u00 x000 1000 = 0x8888

7. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum UxSTA register register 18-2 (DS61168E)

8. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum ADM_EN (bit 24) 0 = no automatic address detect ADDR (bits 23-16) only matter when bit above is set UTXISEL (bits15-14) 01 = raise interrupt when all chars transmitted UTXINV (bit 13) 0 = UxTX idle state is ‘1’ (if not in IrDA mode) URXEN (bit 12) 1 = UARTx receiver is enabled UTXBRK(bit 11) 0 = send no break {1=send start, 12 ‘0’ and stop} UTXEN(bit 10) 1 = UARTx transmitter is enabled UTXBF(bit 9) 1 = Transmit buffer is full {0 = room for at least 1 char} TRMT(bit 8) 0 = Transmit Shift Register is not empty, tx in progress URXISEL (bit 7-6) 00 = Int flag is asserted while rx buffer not empty ADDEN(bit 5) 0 = Address detect mode disabled RIDLE(bit 4) 0 = Data is being received {1=receiver is idle} PERR(bit 3) 1 = Parity error detected for current character FERR(bit 2) 1 = Framing error detected for current character OERR(bit 1) 1 = Receiver buffer overrun. Can only be cleared in s/w URXDA(bit 0) 1 = Receive buffer data available, at least one char. Important BITs of UxSTA e.g. U2STA = 0x1400;

9. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum In the DP32 it is simpler to use UART2 – it shares pins with the I2C pins going to JP4 & 5 Use UART2 and PPS -> U2TX/RPB9 U2RX/RPB8 NB Remove jumpers JP4 & 5 And do not insert IC2C, the 8 pin chip

10. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum You need to program which pins go where – look up Peripheral Pin Select (PPS) in the datasheet. Also the PPS LOCK and UNLOCK sequences.

11. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Next 4 slides give working code; create a project called UART_1 and either wire RB8 and RB9 to a USB TTL 3.3V Usart, or a PICKIT2 or to another DP32 - but wire RB8_board1 to RB9_board2 And RB9_board2 to RB8_board2 (on the PC run PUTTY or PICKIT2 v2.6.1 (NOT PICKIT3 s/w!)

12. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Code to demo serial i/o Modified from http://umassamherstm5.org/tech-tutorials/pic32-tutorials/pic32mx220-tutorials/uart-to-serial-terminalhttp://umassamherstm5.org/tech-tutorials/pic32-tutorials/pic32mx220-tutorials/uart-to-serial-terminal

13. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum NB remove JP4 and JP5 (rotate 180 degrees) Modified from http://umassamherstm5.org/tech-tutorials/pic32-tutorials/pic32mx220-tutorials/uart-to-serial-terminalhttp://umassamherstm5.org/tech-tutorials/pic32-tutorials/pic32mx220-tutorials/uart-to-serial-terminal

14. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Modified from http://umassamherstm5.org/tech-tutorials/pic32-tutorials/pic32mx220-tutorials/uart-to-serial-terminalhttp://umassamherstm5.org/tech-tutorials/pic32-tutorials/pic32mx220-tutorials/uart-to-serial-terminal

15. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Modified from http://umassamherstm5.org/tech-tutorials/pic32-tutorials/pic32mx220-tutorials/uart-to-serial-terminalhttp://umassamherstm5.org/tech-tutorials/pic32-tutorials/pic32mx220-tutorials/uart-to-serial-terminal

16. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Exercises  Send data every second to another DP32 and display it there. (The sending board can be called DP32_1 and the receiver DP32_2)  Send data only when a pushbutton on DP32_1 is pressed.  Send data only when the receiving end says it is ready. (hint wire another wire from a spare i/o line from Dp32_2 to DP32_1.  Use LEDs to show various things

17. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Timer delays  These can use an interrupt – see notes for a 1 second ISR using a flag variable that main polls.  A simple delay is a “blocking” wait. E.g #define DELAY 39062 // assuming 40Mhz clock … // In main near start T1CON = 0x8030; // prescale 256:1, 40Mhz=25nSec and 25/256=> 6.4usec Then for a delay use in your code the following two lines (or put in a function) TMR1=0;PR1=0xFFFF; // Note the 39062 gives a slight inaccuracy. while(TMR1 < DELAY){;}// wait here for 39062 * 6.4uSecs // you arrive here after a quarter second…(reasonably accurate…)

18. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum You can also use the plib library (this code needs modified for the DP32! Do not use as is PPSUnLock; // Allow PIN Mapping PPSOutput(4, RPB10, U2TX); // MAP Tx to PB10 PPSInput (2, U2RX, RPB11); // MAP Rx to PB11 PPSLock; // Prevent Accidental Mapping // Configure UART2 UARTConfigure(UART2, UART_ENABLE_PINS_TX_RX_ONLY); UARTSetLineControl(UART2,UART_DATA_SIZE_8_BITS | UART_PARITY_NONE | UART_STOP_BITS_1); UARTSetDataRate(UART2, GetPeripheralClock(), BaudRate); UARTEnable(UART2,UART_ENABLE_FLAGS(UART_PERIPHERAL | UART_RX | UART_TX)); This code is explained at http://www.eevblog.com/forum/microcontrollers/pic32mx-quickstart/15/

19. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Print a message Function using plib void Serial_print(char *buffer) { while(*buffer != (char)0) { while(!UARTTransmitterIsReady(UART2)); UARTSendDataByte(UART2, *buffer++); } while(!UARTTransmissionHasCompleted(UART2)); UARTSendDataByte(UART2, '\r'); UARTSendDataByte(UART2, '\n'); } This code is explained at http://www.eevblog.com/forum/microcontrollers/pic32mx-quickstart/15/

20. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Sending and Receiving Data using handshake lines – CTS and RTS (manually) int putU2( int c) { while ( CTS); // wait for !CTS, clear to send while ( U2STAbits.UTXBF); // wait while Tx buffer full U2TXREG = c; return c; } // putU2 char getU2( void) { RTS = 0; // assert Request To Send !RTS while ( !U2STAbits.URXDA); // wait for a new char to arrive RTS = 1; return U2RXREG; // read char from receive buffer }// getU2 Could be worth adding the lines, just before the return c; while( !U2STAbits.TRMT);

21. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Serial terminal programs on the PC  Hyperterminal – pre windows 7 in all versions  RealTerm - most excellent, doesn’t work W8  Putty – usually used for network login  MPIDE has a good serial monitor Use USB to serial convertors if the PC has no serial ports  PICKit 2 can do USB to Serial conversion (but not yet working on the PICKit 3) Select 3.3V before plugging in.  You can buy USB to Serial convertors, either full RS232 or just TTL UART. Be careful you do not damage the board! You want 3.3Volts maximum Also several I have used output on pins labelled RCV and input on TX – I had to use a scope to check!

22. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum HyperTerminal Setup (windows XP only)

23. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum RealTerm runs on XP and windows 7 (but not 8)

24. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum PUTTY can perform serial terminal functions When programming the PIC32 and with the UART output connected to Putty many random characters are sent from the PIC to PUTTY. If the handshaking is left at the default XON/XOFF then PUTTY may receive a XOFF (control-S) from the PIC and you have to quit and restart PUTTY after every programming Alternatively select the correct handshaking protocol. Such as clicking on the Serial menu option and selecting “NONE” or “HARDWARE RTS/CTS” Use the Device manager to check the COM port of the USB- TTL adaptor Ensure the Speed is correct

25. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum PICKit2 comes with UART Software – NB NOT the PICKit3 (yet) Wire up the PICKit2 as PICKit Pin 1 - No Connection PICKit Pin 2 - 3V3 PICKit Pin 3 - GND PICKit Pin 4 – DP32 Pin 7 (Tx) RB14 PICKit Pin 5 - DP32 Pin 10 (Rx) RA1 PICKit Pin 6 - No Connection Start the PICKit 2 application and select Tools-->UART Tool

26. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum The PICKit2 has other uses; You can also use the Logic Analyzer Mode. Click 'Exit UART Tool' and start the Logic Tool Select 'Analyser' if it is not on by default. Set the Sample rate to 100 Khz and the Trigger to Ch1 \ (falling edge) Click Capture and, When your code sends 'Hello World!' you should see…

27. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Tips and Tricks To re-direct the output stream of the standard C library (stdio.h) functions such as printf() to a UART:  Define the function: _mon_putc()  Note that a “weak” definition is already provided in the library to send the default output stream (stdout) to UART2 (convenient for all Explorer16 users).  Similarly define: _mon_getc()  A default “weak” version is already provided in the library as well, connecting UART2 receiver to the input stream (stdin).  Weak means that the compiler won’t complain when you define a new function with the same name, it will simply replace it with the new one you provide. NOTE  You are responsible for the UART initialization!  Before the first call to any stdio function (printf()…) make sure the UART2 is enabled and the baud rate is set correctly.

28. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum Code for serial i/o, allowing printf & puts By adding a function called _mon_putc() the linker will use it for calls to printf() and puts()

29. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum

30. Once you define _mon_putc() any call to printf or puts will just work

31. From : Di Jasio - Programming 32-bit Microcontrollers in C with additions by Ian McCrum I couldn’t get it working for _mon_getc() – I expected gets to work… instead use code below