I am deploying 915Mhz HWs at 1200Baud. It seems like I never get an RSSI that is weaker than about 90db. I am hoping to receive packets that are down to 120db. Is there a setting I should use to get maximum sensitivity? I noticed one -90 setting for CMSA or some such thing in the .h file. I changed that to 119, but it did not seem to have any effect.
You mean weaker stronger than -90dbm?
To change the RSSI threshold look for this line - note there is a formula involved, you might want to check the datasheet (http://www.semtech.com/images/datasheet/sx1231h.pdf) for more details:
/* 0x29 */ { REG_RSSITHRESH, 220 }, // must be set to dBm = (-Sensitivity / 2), default is 0xE4 = 228 so -114dBm