We used LPM1 of cc220 to save energy without any problem. When we tried to use LPM2 to further reduce the power, packet reception is good, but only the very first packet transmission works. The following transmissions all fail. Before each failed transmission, the status register is 0xff,which is unexpected. I really appreciate it if you could tell us any insights or suggestion.
FYI, we've followed the steps in Figure 7 of the datasheet and I'm listing the procedures we took below.
Thank you in advance,
To get into LPM2 mode from active mode:
3. VREG_EN=0 // GPIO5 is always set to 0 by MCU
4. Set the MISO pin of the MCU to 0 as output, based on section 10.4 of the datasheet
To move from LPM2 mode to active mode:
1. resume the previous status of the MISO pin of the MCU
2. RESETn=0, VREG_EN=1
3. wait for 0.15ms in order to get regulator stabilized
4. RESETn=1, CSn=0
5. wait till MISO become 1
6. CSn =1
7. resume the cc2520 registers by repeating the settings we did during cc2520 initialization in the bootup stage: TXCTRL, TXPOWER, GPIOCTRL0, GPIOCTRL3, CCACTRL0, MDMCTRL0, MDMCTRL1, RXCTRL, FSCTRL, FSCAL1, AGCCTRL1, AGCCTRL2, EXTCLOCK, ADCTEST0, ADCTEST1, ADCTEST2, FRMCTRL0, FRMFILT0, FRMCTRL1, FIFOPCTRL, pan_id, shortaddress, longaddress and channel.
8. send SRXON to cc2520
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