Heartrate with Coded PHY example from nRF Connect SDK with nRF52833 - Range is disappointing

[Felix Cormier]

Hi,

I am using two Fanstel BM833 dev kits which feature an nRF52833 to test the coded PHY feature. The advertised range is up to 1500m line of sight with the PCB antenna. I used the "peripheral_hr_coded" and "central_hr_coded" examples from the nRF Connect SDK. As-is, this code gives me a range of about 100-150m line-of-sight before the terminal tells me it lost the connection.

• What could make me increase the range further from this example? I saw a few mentions of increasing the output power but it's not clear to me where to set that.
• Also, is the heartrate example optimized for range or are there ways to increase the range further?

1-way communication (peripheral to central only) is acceptable in our application. An example that is optimized for range would be fantastic to evaluate the potential quickly!

Thanks for your help

[Susheel Nuguru]

I am really sorry that i got stuck on the softdevice API even though you clearly mentioned nRF Connect SDK.

Felix Cormier said:

Ensure the connection is really coded phy

bt_conn_get_info will give you info where you can check info->le->phy to know which phy you have tx and rx on.
You can also do a force bt_conn_le_phy_update to coded phy just after the connection just to be sure.

Felix Cormier said:

Adjust the TX power

I normally use this code snippet in my hobby testing projects. It might be helpful to you in your case.

static void set_tx_power(uint8_t handle_type, uint16_t handle, int8_t tx_pwr_lvl)
{
	struct bt_hci_cp_vs_write_tx_power_level *cp;
	struct bt_hci_rp_vs_write_tx_power_level *rp;
	struct net_buf *buf, *rsp = NULL;
	int err;

	buf = bt_hci_cmd_create(BT_HCI_OP_VS_WRITE_TX_POWER_LEVEL,
				sizeof(*cp));
	if (!buf) {
		printk("Unable to allocate command buffer\n");
		return;
	}

	cp = net_buf_add(buf, sizeof(*cp));
	cp->handle = sys_cpu_to_le16(handle);
	cp->handle_type = handle_type;
	cp->tx_power_level = tx_pwr_lvl;

	err = bt_hci_cmd_send_sync(BT_HCI_OP_VS_WRITE_TX_POWER_LEVEL,
				   buf, &rsp);
	if (err) {
		uint8_t reason = rsp ?
			((struct bt_hci_rp_vs_write_tx_power_level *)
			  rsp->data)->status : 0;
		printk("Set Tx power err: %d reason 0x%02x\n", err, reason);
		return;
	}

	rp = (void *)rsp->data;
	printk("Actual Tx Power: %d\n", rp->selected_tx_power);

	net_buf_unref(rsp);
}