RE: ESB - net datarate with 2 MBit/s on-air data rate

Håkon Alseth — Thu, 06 Aug 2026 16:11:23 GMT

Hi Stefan,

The overall RF payload will look something like this:

So if we sum up the total on-air bytes, it will be approx. 5-10 bytes of overhead, depending on your settings.

The on-air time will then be:

40 us + 4 us per byte * (66 + 5) = 324 us

Note that this excludes CPU handling, so the overall timing number will be higher than this.

You have setup 320 us as the timing signal, wanting approx. 3125 payloads of 66 byte user data per second.

On 2 MBit, I measure approx. 2679 payloads of 66 bytes each per second.

Is a latency of 320 us per received payload a hard requirement for you?

You can adjust the payload size to "#define NUM_SAMPLES 3*16U" and set prj.conf::CONFIG_ESB_MAX_PAYLOAD_LENGTH=252, which should allow you to send one RF payload of 194 bytes (2+3*64) every 3*320 us at 2 MBit data rate.

PS:

I added a 1 sec timer, just to push the byte counter, and moved your semaphore for testing. Here is a patch:

diff --git a/esb_ptx/src/main.c b/esb_ptx/src/main.c
index 0942c7a..9802e81 100644
--- a/esb_ptx/src/main.c
+++ b/esb_ptx/src/main.c
@@ -35,7 +35,7 @@ LOG_MODULE_REGISTER(esb_ptx, CONFIG_ESB_PTX_APP_LOG_LEVEL);
 
 #define ESB_RF_CHANNEL 10U
 
-#define NUM_SAMPLES 16U
+#define NUM_SAMPLES 3*16U
 typedef struct {
     uint16_t left;
     uint16_t right;
@@ -48,7 +48,11 @@ typedef struct {
 
 static struct esb_payload tx_payload = {0};
 static void sample_handler(struct k_timer* timer);
+static void esb_throughput_handler(struct k_timer* timer);
+
 K_TIMER_DEFINE(sample_timer, sample_handler, NULL);
+K_TIMER_DEFINE(timer, esb_throughput_handler, NULL);
+
 static K_SEM_DEFINE(tx_sem, 1, CONFIG_ESB_TX_FIFO_SIZE);
 static int packets_handed_over = 0;
 static int packets_sent = 0;
@@ -151,7 +155,7 @@ static int esb_initialize(void) {
     /* PTX Mode, only send. */
     esb_config.protocol = ESB_PROTOCOL_ESB_DPL;
     esb_config.mode = ESB_MODE_PTX;
-    esb_config.bitrate = ESB_BITRATE_4MBPS;
+    esb_config.bitrate = ESB_BITRATE_2MBPS;
     esb_config.crc = ESB_CRC_OFF;
     esb_config.use_fast_ramp_up = true;
     esb_config.payload_length = sizeof(audio_message_t);
@@ -195,9 +199,12 @@ static int esb_initialize(void) {
     return 0;
 }
 
+static uint32_t total_bytes_received;
+
 void event_handler(struct esb_evt const* event) {
     switch (event->evt_id) {
         case ESB_EVENT_TX_SUCCESS:
+            total_bytes_received += sizeof(audio_message_t);
             if (packets_sent % 2) {
                 dk_set_led(PACKET_SENT, 0);
             } else {
@@ -212,9 +219,17 @@ void event_handler(struct esb_evt const* event) {
             LOG_DBG("Packet received");
             break;
     }
+    k_sem_give(&tx_sem);
 }
 
-static void sample_handler(struct k_timer* timer) { k_sem_give(&tx_sem); }
+static void sample_handler(struct k_timer* timer) {  }
+static void esb_throughput_handler(struct k_timer* timer)
+{
+    static uint32_t prev_byte_ctr;
+    uint32_t diff_byte_ctr = total_bytes_received - prev_byte_ctr;
+    printk("%d\n", diff_byte_ctr);
+    prev_byte_ctr = total_bytes_received;
+}
 
 int main(void) {
     int rc;
@@ -251,7 +266,7 @@ int main(void) {
     LOG_INF("Sending test packet");
 
     k_timer_start(&sample_timer, K_USEC(320), K_USEC(320));
-
+    k_timer_start(&timer, K_MSEC(1000), K_MSEC(1000));
     while (1) {
         /* Prepare package. */
         for (int i = 0; i < NUM_SAMPLES; i++) {

Kind regards,

Håkon