Hi everyone
We have a custom made board with NRF52832 chip. We are send it to FCC test lab and they told us the occupied bandwidth (OBW) is too small, 940kHz less than 1MHz. Please see the attached picure for details. When run this test we use the following setup for the radio:
void radio_modulated_tx_carrier(uint8_t txpower, uint8_t mode, uint8_t channel) {
radio_disable();
generate_modulated_rf_packet();
NRF_RADIO->SHORTS = RADIO_SHORTS_END_DISABLE_Msk | RADIO_SHORTS_READY_START_Msk | \
RADIO_SHORTS_DISABLED_TXEN_Msk;;
NRF_RADIO->TXPOWER = (txpower << RADIO_TXPOWER_TXPOWER_Pos);
NRF_RADIO->MODE = (mode << RADIO_MODE_MODE_Pos);
NRF_RADIO->FREQUENCY = channel;
NRF_RADIO->TASKS_TXEN = 1;
}
oid generate_modulated_rf_packet(void) { uint8_t i;
NRF_RADIO->PREFIX0 = rnd8();
NRF_RADIO->BASE0 = rnd32();
// Packet configuration:
// S1 size = 0 bits, S0 size = 0 bytes, payload length size = 8 bits
NRF_RADIO->PCNF0 = (0UL << RADIO_PCNF0_S1LEN_Pos) |
(0UL << RADIO_PCNF0_S0LEN_Pos) |
(8UL << RADIO_PCNF0_LFLEN_Pos);
// Packet configuration:
// Bit 25: 1 Whitening enabled
// Bit 24: 1 Big endian,
// 4 byte base address length (5 byte full address length),
// 0 byte static length, max 255 byte payload .
NRF_RADIO->PCNF1 = (RADIO_PCNF1_WHITEEN_Enabled << RADIO_PCNF1_WHITEEN_Pos) |
(RADIO_PCNF1_ENDIAN_Big << RADIO_PCNF1_ENDIAN_Pos) |
(4UL << RADIO_PCNF1_BALEN_Pos) |
(0UL << RADIO_PCNF1_STATLEN_Pos) |
(255UL << RADIO_PCNF1_MAXLEN_Pos);
NRF_RADIO->CRCCNF = (RADIO_CRCCNF_LEN_Disabled << RADIO_CRCCNF_LEN_Pos);
r_test.packet[0] = 254; // 254 byte payload.
// Fill payload with random data.
for (i = 0; i < 254; i++)
{
r_test.packet[i + 1] = rnd8();
}
NRF_RADIO->PACKETPTR = (uint32_t)r_test.packet;
}
Thanks
