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sys/net/loramac: move lora time on air compute helper in loramac.h

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This commit is contained in:
Alexandre Abadie 2021-03-13 20:41:25 +01:00
parent f337a9025a
commit 05224adc96
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GPG Key ID: 1C919A403CAE1405
2 changed files with 50 additions and 38 deletions
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49
sys/include/net/loramac.h
View File

@ -22,6 +22,7 @@
#ifndef NET_LORAMAC_H
#define NET_LORAMAC_H
#include <assert.h>
#include <stdint.h>
#include <stdlib.h>
@ -966,6 +967,54 @@ typedef enum {
uint8_t dcycle; /**< Duty cycle to use on this channel (1 to 100) */
} loramac_channel_t;
/**
* @brief Compute the time on air of a LoRa packet
*
* This function uses a precomputed table to calculate time on air without
* using floating point arithmetic
*
* @param[in] pkt_len Length of a packet in bytes
* @param[in] dr Datarate used to send the packet
* @param[in] cr Coding rate used to send the packet
* @return time on air in us
*/
static inline uint32_t lora_time_on_air(size_t pkt_len, uint8_t dr, uint8_t cr)
{
assert(dr <= LORAMAC_DR_6);
const uint8_t _K[6][4] = {
{ 0, 1, 5, 5 }, /* DR0 */
{ 0, 1, 4, 5 }, /* DR1 */
{ 1, 5, 5, 5 }, /* DR2 */
{ 1, 4, 5, 4 }, /* DR3 */
{ 1, 3, 4, 4 }, /* DR4 */
{ 1, 2, 4, 3 } /* DR5 */
};
uint32_t t_sym = 1 << (15 - dr);
uint32_t t_preamble = (t_sym << 3) + (t_sym << 2) + (t_sym >> 2);
uint8_t index = (dr < LORAMAC_DR_6) ? dr : LORAMAC_DR_5;
uint8_t n0 = _K[index][0];
uint32_t nb_symbols;
uint8_t offset = _K[index][1];
if (pkt_len < offset) {
nb_symbols = 8 + n0 * (cr + 4);
}
else {
uint8_t c1 = _K[index][2];
uint8_t c2 = _K[index][3];
uint8_t pos = (pkt_len - offset) % (c1 + c2);
uint8_t cycle = (pkt_len - offset) / (c1 + c2);
nb_symbols = 8 + (n0 + 2 * cycle + 1 + (pos > (c1 - 1))) * (cr + 4);
}
uint32_t t_payload = t_sym * nb_symbols;
return t_preamble + t_payload;
}
#ifdef __cplusplus
}
#endif

39
sys/net/gnrc/link_layer/lorawan/gnrc_lorawan.c
View File

@ -207,43 +207,6 @@ void gnrc_lorawan_radio_rx_timeout_cb(gnrc_lorawan_t *mac)
_sleep_radio(mac);
}
/* This function uses a precomputed table to calculate time on air without
* using floating point arithmetic */
static uint32_t lora_time_on_air(size_t payload_size, uint8_t dr, uint8_t cr)
{
assert(dr <= LORAMAC_DR_6);
uint8_t _K[6][4] = { { 0, 1, 5, 5 },
{ 0, 1, 4, 5 },
{ 1, 5, 5, 5 },
{ 1, 4, 5, 4 },
{ 1, 3, 4, 4 },
{ 1, 2, 4, 3 } };
uint32_t t_sym = 1 << (15 - dr);
uint32_t t_preamble = (t_sym << 3) + (t_sym << 2) + (t_sym >> 2);
int index = (dr < LORAMAC_DR_6) ? dr : LORAMAC_DR_5;
uint8_t n0 = _K[index][0];
int nb_symbols;
uint8_t offset = _K[index][1];
if (payload_size < offset) {
nb_symbols = 8 + n0 * cr;
}
else {
uint8_t c1 = _K[index][2];
uint8_t c2 = _K[index][3];
uint8_t pos = (payload_size - offset) % (c1 + c2);
uint8_t cycle = (payload_size - offset) / (c1 + c2);
nb_symbols = 8 + (n0 + 2 * cycle + 1 + (pos > (c1 - 1))) * cr;
}
uint32_t t_payload = t_sym * nb_symbols;
return t_preamble + t_payload;
}
void gnrc_lorawan_send_pkt(gnrc_lorawan_t *mac, iolist_t *psdu, uint8_t dr)
{
netdev_t *dev = gnrc_lorawan_get_netdev(mac);
@ -260,7 +223,7 @@ void gnrc_lorawan_send_pkt(gnrc_lorawan_t *mac, iolist_t *psdu, uint8_t dr)
dev->driver->get(dev, NETOPT_CODING_RATE, &cr, sizeof(cr));
mac->toa = lora_time_on_air(iolist_size(psdu), dr, cr + 4);
mac->toa = lora_time_on_air(iolist_size(psdu), dr, cr);
if (dev->driver->send(dev, psdu) == -ENOTSUP) {
DEBUG("gnrc_lorawan: Cannot send: radio is still transmitting");