1 2 3 #define ITM_ENA (*(volatile unsigned int*)0xE0000E00) // ITM Enable 4 #define ITM_TPR (*(volatile unsigned int*)0xE0000E40) // Trace Privilege Register 5 #define ITM_TCR (*(volatile unsigned int*)0xE0000E80) // ITM Trace Control Reg. 6 #define ITM_LSR (*(volatile unsigned int*)0xE0000FB0) // ITM Lock Status Register 7 #define DHCSR (*(volatile unsigned int*)0xE000EDF0) // Debug register 8 #define DEMCR (*(volatile unsigned int*)0xE000EDFC) // Debug register 9 #define TPIU_ACPR (*(volatile unsigned int*)0xE0040010) // Async Clock presacler register 10 #define TPIU_SPPR (*(volatile unsigned int*)0xE00400F0) // Selected Pin Protocol Register 11 #define DWT_CTRL (*(volatile unsigned int*)0xE0001000) // DWT Control Register 12 #define FFCR (*(volatile unsigned int*)0xE0040304) // Formatter and flush Control Register 13 // 14 // STIM word and byte acces 15 #define ITM_STIM_U32 (*(volatile unsigned int*)0xE0000000) 16 #define ITM_STIM_U8 (*(volatile char*)0xE0000000) 17 18 // The stimulus port from which SWO data is received and displayed. 19 unsigned int ITM_PORT_BIT0 = 0; 20 21 // Has to be calculated according to the CPU speed and the output baud rate 22 unsigned int TargetDiv = 1; 23 24 void SWO_Enable( void ) 25 { 26 unsigned int StimulusRegs; 27 // 28 // Enable access to SWO registers 29 // 30 DEMCR |= ( 1 << 24 ); 31 ITM_LSR = 0xC5ACCE55; 32 // 33 // Initially disable ITM and stimulus port 34 // To make sure that nothing is transferred via SWO 35 // when changing the SWO prescaler etc. 36 // 37 StimulusRegs = ITM_ENA; 38 StimulusRegs &= ~( 1 << ITM_PORT_BIT0 ); 39 ITM_ENA = StimulusRegs; // Disable ITM stimulus port 40 ITM_TCR = 0; // Disable ITM 41 42 // 43 // Initialize SWO (prescaler, etc.) 44 // 45 TPIU_SPPR = 0x00000002; // Select NRZ mode 46 TPIU_ACPR = TargetDiv - 1; // Example: 72/48 = 1,5 MHz 47 ITM_TPR = 0x00000000; 48 DWT_CTRL = 0x400003FE; 49 FFCR = 0x00000100; 50 // 51 // Enable ITM and stimulus port 52 // 53 ITM_TCR = 0x1000D; // Enable ITM 54 ITM_ENA = StimulusRegs | ( 1 << ITM_PORT_BIT0 ); // Enable ITM stimulus port 55 } 56 57 // Prints a character to the ITM_STIM register in order to provide data for SWO 58 void SWO_PrintChar( char c ) 59 { 60 // Check if SWO is set up. If it is not, 61 // return to avoid that a program hangs if no debugger is connected. 62 // 63 // Check if DEBUGEN in DHCSR is set 64 // 65 if ( ( DHCSR & 1 ) != 1 ) 66 return; 67 68 // 69 // Check if TRACENA in DEMCR is set 70 // 71 if ( ( DEMCR & ( 1 << 24 ) ) == 0 ) 72 return; 73 74 // 75 // Check if ITM_TRC is enabled 76 // 77 if ( ( ITM_TCR & ( 1 << 22 ) ) == 1 ) 78 return; 79 80 // 81 // Check if stimulus port 0 is enabled 82 // 83 if ( ( ITM_ENA & 1 ) == 0 ) 84 return; 85 86 // 87 // Wait until STIMx is ready to accept at least 1 word 88 // 89 while ( ( ITM_STIM_U8 & 1 ) == 0 ) 90 { 91 92 } 93 94 ITM_STIM_U8 = c; 95 } 96 97 // Prints a string via SWO 98 void SWO_PrintString( const char *s ) 99 { 100 // 101 // Print out character per character 102 // 103 while ( *s ) 104 { 105 SWO_PrintChar( *s++ ); 106 } 107 }
JLINK SWO Viewer
Free-of-charge utility for J-Link. Displays the terminal output of the target using the SWO pin.
Can be used in parallel with a debugger or stand-alone.
This is especially useful when using debuggers which do not come with built-in support for SWO.