I2CDriverTest01.h

00001 // A high prio thread reads at a rate of 1kHz from a SRF08 ultrasonic ranger
00002 // data packets of different size, whereas the lower prio main thread measures the CPU time left.
00003 
00004 #include "mbed.h"
00005 #include "rtos.h"
00006 #include "I2CMasterRtos.h"
00007 #include "stdint.h"
00008 
00009 volatile int g_disco=0;
00010 volatile int g_len=2;
00011 volatile int g_freq=100000;
00012 
00013 I2CMasterRtos i2c(p28, p27);
00014 const uint32_t adr = 0x70<<1;
00015 
00016 void highPrioCallBck(void const *args)
00017 {
00018     i2c.frequency(g_freq);
00019     // read back srf08 echo times (1+16 words)
00020     const char reg= 0x02;
00021     char result[64];
00022     uint32_t t1=us_ticker_read();
00023     i2c.read(adr, reg, result, g_len);
00024     uint32_t dt=us_ticker_read()-t1;
00025     uint16_t dst=((static_cast<uint16_t>(result[0])<<8)|static_cast<uint16_t>(result[1]));
00026     if(--g_disco>0) printf("dst=%4dcm dt=%4dus\n",dst,dt);
00027 }
00028 
00029 int doit()
00030 {
00031     RtosTimer highPrioTicker(highPrioCallBck, osTimerPeriodic, (void *)0);
00032 
00033     Thread::wait(500);
00034     // trigger srf08 ranging
00035     const char regNcmd[2]= {0x00,0x54};
00036     i2c.write(adr, regNcmd, 2);
00037     osDelay(200);
00038 
00039     highPrioTicker.start(1);
00040 
00041 #if defined(TARGET_LPC1768)
00042     const int nTest=7;
00043     const int freq[nTest]=  {1e5,   1e5,    1e5,   4e5,    4e5,    4e5,    4e5};
00044     const int len[nTest]=   {1,     4,      6,      1,     6,     12,      25};
00045 #elif defined(TARGET_LPC11U24)
00046     const int nTest=5;
00047     const int freq[nTest]=  {1e5,   1e5,    4e5,   4e5,    4e5    };
00048     const int len[nTest]=   {1,     6,      1,      6,     23};
00049 #endif
00050     for(int i=0; i<nTest; ++i) {
00051         g_freq = freq[i];
00052         g_len = len[i];
00053         printf("f=%d l=%d\n",g_freq,g_len);
00054         Thread::wait(500);
00055         const uint32_t dt=1e6;
00056         uint32_t tStart = us_ticker_read();
00057         uint32_t tLast = tStart;
00058         uint32_t tAct = tStart;
00059         uint32_t tMe=0;
00060         do {
00061             tAct=us_ticker_read();
00062             #if defined(TARGET_LPC1768)
00063             if(tAct==tLast+1)++tMe;
00064             #elif defined(TARGET_LPC11U24)
00065             uint32_t delta = tAct-tLast;
00066             if(delta<=2)tMe+=delta;  // on the 11U24 this loop takes a bit longer than 1µs (ISR ~3µs, task switch ~8µs)
00067             #endif
00068             tLast=tAct;
00069         } while(tAct-tStart<dt);
00070         printf("dc=%5.2f \n", 100.0*(float)tMe/dt);
00071         g_disco=5;
00072         while(g_disco>0);
00073     }
00074     return 0;
00075 }