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drivers/cc2420: calculate CRC and check CRC_OK bit on packet reception

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First start calculating the CRC in hardware when receiving a frame.

Then, other than the at86rf2xx transceivers the cc2420 don't consider the
CRC_OK flag when reporting a successful packet reception. This change
introduces a check for this bit and drops the packet else by flushing
the RX FIFO.
This commit is contained in:
Thomas Eichinger 2016-10-28 14:46:23 -07:00
parent 25e7681c35
commit 103c426cdc
2 changed files with 27 additions and 15 deletions
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39
drivers/cc2420/cc2420.c
View File

@ -94,7 +94,6 @@ int cc2420_init(cc2420_t *dev)
cc2420_set_chan(dev, CC2420_CHAN_DEFAULT);
cc2420_set_txpower(dev, CC2420_TXPOWER_DEFAULT);
/* set default options */
cc2420_set_option(dev, CC2420_OPT_AUTOACK, true);
cc2420_set_option(dev, CC2420_OPT_CSMA, true);
@ -124,15 +123,17 @@ int cc2420_init(cc2420_t *dev)
reg &= ~CC2420_SECCTRL0_RXFIFO_PROT;
cc2420_reg_write(dev, CC2420_REG_SECCTRL0, reg);
/* go into RX state */
cc2420_set_state(dev, CC2420_GOTO_RX);
/* set preamble length to 3 leading zero byte */
/* and turn on hardware CRC generation */
reg = cc2420_reg_read(dev, CC2420_REG_MDMCTRL0);
reg &= ~(CC2420_MDMCTRL0_PREAMBLE_M);
reg |= CC2420_MDMCTRL0_PREAMBLE_3B;
reg |= CC2420_MDMCTRL0_AUTOCRC;
cc2420_reg_write(dev, CC2420_REG_MDMCTRL0, reg);
/* go into RX state */
cc2420_set_state(dev, CC2420_GOTO_RX);
return 0;
}
@ -216,22 +217,21 @@ void cc2420_tx_exec(cc2420_t *dev)
int cc2420_rx(cc2420_t *dev, uint8_t *buf, size_t max_len, void *info)
{
uint8_t len;
uint8_t crc_corr;
/* get the packet length (without dropping it) (first byte in RX FIFO) */
cc2420_ram_read(dev, CC2420_RAM_RXFIFO, &len, 1);
len -= 2; /* subtract RSSI and FCF */
if (!buf) {
/* without a provided buffer, only readout the length and return it */
if (buf == NULL) {
/* get the packet length (without dropping it) (first byte in RX FIFO) */
cc2420_ram_read(dev, CC2420_RAM_RXFIFO, &len, 1);
len -= 2; /* subtract RSSI and FCF */
DEBUG("cc2420: recv: packet of length %i in RX FIFO\n", (int)len);
}
/* if a buffer is given, read (and drop) the packet */
if (buf) {
/* We could the drop length byte here, msp430 platforms don't allow
* empty reads so we don't do it and read the length byte again. */
else {
/* read length byte */
cc2420_fifo_read(dev, &len, 1);
len -=2; /* subtract RSSI and FCF */
len -= 2; /* subtract RSSI and FCF */
/* if a buffer is given, read (and drop) the packet */
len = (len > max_len) ? max_len : len;
/* read fifo contents */
@ -241,6 +241,15 @@ int cc2420_rx(cc2420_t *dev, uint8_t *buf, size_t max_len, void *info)
uint8_t rssi;
cc2420_fifo_read(dev, &rssi, 1);
DEBUG("cc2420: recv: RSSI is %i\n", (int)rssi);
/* fetch and check if CRC_OK bit (MSB) is set */
cc2420_fifo_read(dev, &crc_corr, 1);
if (!(crc_corr & 0x80)) {
DEBUG("cc2420: recv: CRC_OK bit not set, dropping packet\n");
/* drop the corrupted frame from the RXFIFO */
len = 0;
}
/* finally flush the FIFO */
cc2420_strobe(dev, CC2420_STROBE_FLUSHRX);
cc2420_strobe(dev, CC2420_STROBE_FLUSHRX);

3
drivers/include/cc2420.h
View File

@ -304,6 +304,9 @@ void cc2420_tx_exec(cc2420_t *dev);
* @param[out] buf buffer to write data to
* @param[in] max_len number of bytes to read from device
* @param[in] info to be removed
*
* @return the number of bytes in the Rx FIFO
* @return the number of bytes written to @p buf if present
*/
int cc2420_rx(cc2420_t *dev, uint8_t *buf, size_t max_len, void *info);