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fix coverity 294113

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This commit is contained in:
iceman1001 2020-07-11 20:53:07 +02:00
commit ebb7eb9f3e
1 changed files with 31 additions and 40 deletions
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71
armsrc/em4x50.c
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@ -100,7 +100,6 @@ int gLow = 0;
static void init_tag(void) {
// initialize global tag structure
for (int i = 0; i < 34; i++)
for (int j = 0; j < 7; j++)
tag.sectors[i][j] = 0x00;
@ -109,9 +108,7 @@ static void init_tag(void) {
static uint8_t bits2byte(uint8_t *bits, int length) {
// converts <length> separate bits into a single "byte"
uint8_t byte = 0;
for (int i = 0; i < length; i++) {
byte |= bits[i];
@ -124,11 +121,10 @@ static uint8_t bits2byte(uint8_t *bits, int length) {
}
static void msb2lsb_word(uint8_t *word) {
// reorders given <word> according to EM4x50 datasheet (msb -> lsb)
uint8_t buff[4];
buff[0] = reflect8(word[3]);
buff[1] = reflect8(word[2]);
buff[2] = reflect8(word[1]);
@ -141,13 +137,12 @@ static void msb2lsb_word(uint8_t *word) {
}
static void save_word(int pos, uint8_t bits[EM4X50_TAG_WORD]) {
// split "raw" word into data, row and column parity bits and stop bit and
// save them in global tag structure
uint8_t row_parity[4];
uint8_t col_parity[8];
// data and row parities
for (int i = 0; i < 4; i++) {
tag.sectors[pos][i] = bits2byte(&bits[9*i],8);
@ -161,7 +156,7 @@ static void save_word(int pos, uint8_t bits[EM4X50_TAG_WORD]) {
col_parity[i] = bits[36+i];
tag.sectors[pos][5] = bits2byte(col_parity,8);
// stop bit
tag.sectors[pos][6] = bits[44];
}
@ -169,7 +164,7 @@ static void save_word(int pos, uint8_t bits[EM4X50_TAG_WORD]) {
static void wait_timer(int timer, uint32_t period) {
// do nothing for <period> using timer <timer>
if (timer == FPGA_TIMER_0) {
AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;
@ -184,9 +179,8 @@ static void wait_timer(int timer, uint32_t period) {
}
static void em4x50_setup_read(void) {
FpgaDownloadAndGo(FPGA_BITSTREAM_LF);
FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_ADC | FPGA_LF_ADC_READER_FIELD);
// 50ms for the resonant antenna to settle.
@ -195,12 +189,12 @@ static void em4x50_setup_read(void) {
FpgaSetupSsc(FPGA_MAJOR_MODE_LF_READER);
// start a 1.5ticks is 1us
StartTicks();
FpgaSendCommand(FPGA_CMD_SET_DIVISOR, LF_DIVISOR_125);
// Connect the A/D to the peak-detected low-frequency path.
SetAdcMuxFor(GPIO_MUXSEL_LOPKD);
// Steal this pin from the SSP (SPI communication channel with fpga) and
// use it to control the modulation
AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
@ -208,7 +202,7 @@ static void em4x50_setup_read(void) {
// Disable modulation at default, which means enable the field
LOW(GPIO_SSC_DOUT);
// Enable Peripheral Clock for
// TIMER_CLOCK0, used to measure exact timing before answering
// TIMER_CLOCK1, used to capture edges of the tag frames
@ -221,17 +215,17 @@ static void em4x50_setup_read(void) {
// TC0: Capture mode, default timer source = MCK/2 (TIMER_CLOCK1), no triggers
AT91C_BASE_TC0->TC_CMR = AT91C_TC_CLKS_TIMER_DIV1_CLOCK;
// TC1: Capture mode, default timer source = MCK/2 (TIMER_CLOCK1), no triggers
AT91C_BASE_TC1->TC_CMR = AT91C_TC_CLKS_TIMER_DIV1_CLOCK;
// Enable and reset counters
AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN | AT91C_TC_SWTRG;
// synchronized startup procedure
while (AT91C_BASE_TC0->TC_CV > 0) {}; // wait until TC1 returned to zero
// Watchdog hit
WDT_HIT();
}
@ -239,21 +233,21 @@ static void em4x50_setup_read(void) {
// functions for "reader" use case
static bool get_signalproperties(void) {
// calculate signal properties (mean amplitudes) from measured data:
// 32 amplitudes (maximum values) -> mean amplitude value -> gHigh -> gLow
bool signal_found = false;
int no_periods = 32, pct = 75, noise = 140;
uint8_t sample = 0, sample_ref = 127;
uint8_t sample_ref = 127;
uint8_t sample_max_mean = 0;
uint8_t sample_max[no_periods];
uint32_t sample_max_sum = 0;
memcpy(sample_max, 0x00, sizeof(sample_max));
// wait until signal/noise > 1 (max. 32 periods)
for (int i = 0; i < T0 * no_periods; i++) {
// about 2 samples per bit period
wait_timer(0, T0 * EM4X50_T_TAG_HALF_PERIOD);
@ -261,9 +255,9 @@ static bool get_signalproperties(void) {
signal_found = true;
break;
}
}
if (!signal_found)
return false;
@ -273,39 +267,36 @@ static bool get_signalproperties(void) {
AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;
while (AT91C_BASE_TC0->TC_CV < T0 * 3 * EM4X50_T_TAG_FULL_PERIOD) {
sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
volatile uint8_t sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
if (sample > sample_max[i])
sample_max[i] = sample;
}
sample_max_sum += sample_max[i];
}
sample_max_mean = sample_max_sum / no_periods;
// set global envelope variables
gHigh = sample_ref + pct * (sample_max_mean - sample_ref) / 100;
gLow = sample_ref - pct * (sample_max_mean - sample_ref) / 100;
return true;
}
static int get_next_bit(void) {
// returns bit value (or EM4X50_BIT_OTHER -> no bit pattern) by evaluating
// a single sample within a bit period (given there is no LIW, ACK or NAK)
// This function is not used for decoding, it is only used for identifying
// a listen window (return value = EM4X50_BIT_OTHER) in functions
// "find_double_listen_window" and "check_ack"
uint8_t sample;
// get sample at 3/4 of bit period
wait_timer(0, T0 * EM4X50_T_TAG_THREE_QUARTER_PERIOD);
sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
uint8_t sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
// wait until end of bit period
wait_timer(0, T0 * EM4X50_T_TAG_QUARTER_PERIOD);
@ -315,7 +306,7 @@ static int get_next_bit(void) {
return EM4X50_BIT_0;
else if (sample < gLow)
return EM4X50_BIT_1;
return EM4X50_BIT_OTHER;
}