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Merge pull request #367 from oliv3r/respect_pn532_i2c_timing
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Respect pn532 i2c timing
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@neomilium
neomilium committed Dec 5, 2016
2 parents c3b3f64 + d960673 commit b2a9cce
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Showing 2 changed files with 114 additions and 38 deletions.
48 changes: 27 additions & 21 deletions libnfc/chips/pn53x-internal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -81,32 +81,38 @@
#define TgGetTargetStatus 0x8A

/** @note PN53x's normal frame:
* See the PN532 (firmware) user manual, section 6.2.1.1: Normal information
* frame, figure 13. Normal information frame, page 28 rev. 02 - 2007-11-07.
*
* .-- Start
* | .-- Packet length
* | | .-- Length checksum
* | | | .-- Direction (D4 Host to PN, D5 PN to Host)
* | | | | .-- Code
* | | | | | .-- Packet checksum
* | | | | | | .-- Postamble
* V | | | | | |
* ----- V V V V V V
* 00 FF 02 FE D4 02 2A 00
* .-- Preamble
* | .-- Start
* | | .-- Packet length
* | | | .-- Length checksum
* | | | | .-- Direction (D4 Host to PN, D5 PN to Host)
* | | | | | .-- Code
* | | | | | | .-- Packet checksum
* | | | | | | | .-- Postamble
* | V | | | | | |
* V ----- V V V V V V
* 00 00 FF 02 FE D4 02 2A 00
*/

/** @note PN53x's extended frame:
* See the PN532 (firmware) user manual, section 6.2.1.2: Extended information
* frame, figure 14. Normal information frame, page 29 rev. 02 - 2007-11-07.
*
* .-- Start
* | .-- Fixed to FF to enable extended frame
* | | .-- Packet length
* | | | .-- Length checksum
* | | | | .-- Direction (D4 Host to PN, D5 PN to Host)
* | | | | | .-- Code
* | | | | | | .-- Packet checksum
* | | | | | | | .-- Postamble
* V V V | | | | |
* ----- ----- ----- V V V V V
* 00 FF FF FF 00 02 FE D4 02 2A 00
* .-- Preamble
* | .-- Start
* | | .-- Fixed to FF to enable extended frame
* | | | .-- Packet length
* | | | | .-- Length checksum
* | | | | | .-- Direction (D4 Host to PN, D5 PN to Host)
* | | | | | | .-- Code
* | | | | | | | .-- Packet checksum
* | | | | | | | | .-- Postamble
* | V V V | | | | |
* V ----- ----- ----- V V V V V
* 00 00 FF FF FF 00 02 FE D4 02 2A 00
*/

/**
Expand Down
104 changes: 87 additions & 17 deletions libnfc/drivers/pn532_i2c.c
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,13 @@
// I2C address of the PN532 chip.
#define PN532_I2C_ADDR 0x24

/*
* When sending lots of data, the pn532 occasionally fails to respond in time.
* Since it happens so rarely, lets try to fix it by re-sending the data. This
* define allows for fine tuning the number of retries.
*/
#define PN532_SEND_RETRIES 3

// Internal data structs
const struct pn53x_io pn532_i2c_io;

Expand All @@ -67,13 +74,9 @@ struct pn532_i2c_data {
volatile bool abort_flag;
};

/* Delay for the loop waiting for READY frame (in ms) */
#define PN532_RDY_LOOP_DELAY 90

const struct timespec rdyDelay = {
.tv_sec = 0,
.tv_nsec = PN532_RDY_LOOP_DELAY * 1000 * 1000
};
/* preamble and start bytes, see pn532-internal.h for details */
const uint8_t pn53x_preamble_and_start[] = { 0x00, 0x00, 0xff };
#define PN53X_PREAMBLE_AND_START_LEN (sizeof(pn53x_preamble_and_start) / sizeof(pn53x_preamble_and_start[0]))

/* Private Functions Prototypes */

Expand All @@ -96,6 +99,70 @@ static size_t pn532_i2c_scan(const nfc_context *context, nfc_connstring connstri

#define DRIVER_DATA(pnd) ((struct pn532_i2c_data*)(pnd->driver_data))

/*
* Bus free time (in ms) between a STOP condition and START condition. See
* tBuf in the PN532 data sheet, section 12.25: Timing for the I2C interface,
* table 320. I2C timing specification, page 211, rev. 3.2 - 2007-12-07.
*/
#define PN532_BUS_FREE_TIME 1.3
static struct timespec __transaction_stop;

/**
* @brief Wrapper around i2c_read to ensure proper timing by respecting the
* minimal free bus time between a STOP condition and a START condition.
*
* @note This is not thread safe, but since libnfc is single threaded
* this should be okay.
*
* @param id I2C device
* @param buf pointer on buffer used to store data
* @param len length of the buffer
* @return length (in bytes) of read data, or driver error code (negative value)
*/
static ssize_t pn532_i2c_read(const i2c_device id,
uint8_t *buf, const size_t len)
{
struct timespec transaction_start, bus_free_time = { 0 };
ssize_t ret;

clock_gettime(CLOCK_MONOTONIC, &transaction_start);
bus_free_time.tv_nsec = (PN532_BUS_FREE_TIME * 1000 * 1000) -
(transaction_start.tv_nsec - __transaction_stop.tv_nsec);
nanosleep(&bus_free_time, NULL);

ret = i2c_read(id, buf, len);
clock_gettime(CLOCK_MONOTONIC, &__transaction_stop);
return ret;
}

/**
* @brief Wrapper around i2c_write to ensure proper timing by respecting the
* minimal free bus time between a STOP condition and a START condition.
*
* @note This is not thread safe, but since libnfc is single threaded
* this should be okay.
*
* @param id I2C device
* @param buf pointer on buffer containing data
* @param len length of the buffer
* @return NFC_SUCCESS on success, otherwise driver error code
*/
static ssize_t pn532_i2c_write(const i2c_device id,
const uint8_t *buf, const size_t len)
{
struct timespec transaction_start, bus_free_time = { 0 };
ssize_t ret;

clock_gettime(CLOCK_MONOTONIC, &transaction_start);
bus_free_time.tv_nsec = (PN532_BUS_FREE_TIME * 1000 * 1000) -
(transaction_start.tv_nsec - __transaction_stop.tv_nsec);
nanosleep(&bus_free_time, NULL);

ret = i2c_write(id, buf, len);
clock_gettime(CLOCK_MONOTONIC, &__transaction_stop);
return ret;
}

/**
* @brief Scan all available I2C buses to find PN532 devices.
*
Expand Down Expand Up @@ -308,6 +375,7 @@ static int
pn532_i2c_send(nfc_device *pnd, const uint8_t *pbtData, const size_t szData, int timeout)
{
int res = 0;
uint8_t retries;

// Discard any existing data ?

Expand All @@ -334,15 +402,22 @@ pn532_i2c_send(nfc_device *pnd, const uint8_t *pbtData, const size_t szData, int
break;
};

uint8_t abtFrame[PN532_BUFFER_LEN] = { 0x00, 0x00, 0xff }; // Every packet must start with "00 00 ff"
uint8_t abtFrame[PN532_BUFFER_LEN];
size_t szFrame = 0;

memcpy(abtFrame, pn53x_preamble_and_start, PN53X_PREAMBLE_AND_START_LEN); // Every packet must start with the preamble and start bytes.
if ((res = pn53x_build_frame(abtFrame, &szFrame, pbtData, szData)) < 0) {
pnd->last_error = res;
return pnd->last_error;
}

res = i2c_write(DRIVER_DATA(pnd)->dev, abtFrame, szFrame);
for (retries = PN532_SEND_RETRIES; retries > 0; retries--) {
res = pn532_i2c_write(DRIVER_DATA(pnd)->dev, abtFrame, szFrame);
if (res >= 0)
break;

log_put(LOG_GROUP, LOG_CATEGORY, NFC_LOG_PRIORITY_ERROR, "Failed to transmit data. Retries left: %d.", retries - 1);
}

if (res < 0) {
log_put(LOG_GROUP, LOG_CATEGORY, NFC_LOG_PRIORITY_ERROR, "%s", "Unable to transmit data. (TX)");
Expand Down Expand Up @@ -400,10 +475,7 @@ pn532_i2c_wait_rdyframe(nfc_device *pnd, uint8_t *pbtData, const size_t szDataLe
}

do {
// Wait a little bit before reading
nanosleep(&rdyDelay, (struct timespec *) NULL);

int recCount = i2c_read(DRIVER_DATA(pnd)->dev, i2cRx, szDataLen + 1);
int recCount = pn532_i2c_read(DRIVER_DATA(pnd)->dev, i2cRx, szDataLen + 1);

if (DRIVER_DATA(pnd)->abort_flag) {
// Reset abort flag
Expand Down Expand Up @@ -477,9 +549,7 @@ pn532_i2c_receive(nfc_device *pnd, uint8_t *pbtData, const size_t szDataLen, int
goto error;
}

const uint8_t pn53x_preamble[3] = { 0x00, 0x00, 0xff };

if (0 != (memcmp(frameBuf, pn53x_preamble, 3))) {
if (0 != (memcmp(frameBuf, pn53x_preamble_and_start, PN53X_PREAMBLE_AND_START_LEN))) {
log_put(LOG_GROUP, LOG_CATEGORY, NFC_LOG_PRIORITY_ERROR, "%s", "Frame preamble+start code mismatch");
pnd->last_error = NFC_EIO;
goto error;
Expand Down Expand Up @@ -572,7 +642,7 @@ pn532_i2c_receive(nfc_device *pnd, uint8_t *pbtData, const size_t szDataLen, int
int
pn532_i2c_ack(nfc_device *pnd)
{
return i2c_write(DRIVER_DATA(pnd)->dev, pn53x_ack_frame, sizeof(pn53x_ack_frame));
return pn532_i2c_write(DRIVER_DATA(pnd)->dev, pn53x_ack_frame, sizeof(pn53x_ack_frame));
}

/**
Expand Down

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