I’m evaluating both the RAK3172 and RAK3172-SIP for what RAKwireless refers to as “low-level development”.
There is a “low-level” document, but at the time of writing it seems to be specific to the RAK3172 (non-SIP). I’d link to it, but the forum prevents me.
On that page, there is a “Low Level Development zip file” link that was clearly written only for crystal (not TCXO) usage (e.g. for the non-SIP module).
That is straightforward to change, but given the power consumption measurements that I am seeing, I am suspicious that there are other changes that need to be made.
Using the “RUI” firmware that RAKwireless provides, it is possible to operate the module in receive and transmit to measure power consumption:
(followed by an ATZ to end receive)
(followed by an ATZ to end transmit)
where the second argument “0” can be changed for different power levels.
Here are the current measurements all obtained with a calibrated 6.5 digit bench multimeter in statistics average mode (30 samples with high TX power, 50 samples with medium TX power, and 100 samples for RX):
For comparison, here are the numbers I get doing the equivalent with the Semtech library:
- My implementation is more efficient in receive than RUI (probably just because of a lower CPU clock speed); the same improvement can also be seen for transmit for non-SIP only
- The SIP module draws more current in receive than the non-SIP module (extra consumption due to TCXO?)
- There does not seem to be big difference with RUI for transmit, but yet my Semtech-based code draw substantially more current.
- The 20dBm numbers are higher than the RAKwireless datasheet, but those are only quoted for 868MHz.
#2 makes me wonder if the RAKwireless datasheet “Electrical Characteristics” are accurate, since they claim identical receive performance between the non-SIP and SIP:
#3 makes me suspect that there are other changes between the RAK3272 (non-SIP) and RAK3272-SIP that need to be documented.
For comparison, here are the same numbers using the ST NUCLEO WL55JC1:
The lower current draw at lower transmit power is likely due to ST supporting the low-power PA in addition to the high-power PA. The RAK3272 (non-SIP or SIP) design is only using the high-power PA.
It is not clear to me why the RAK3272 is less efficient at 20dBm; this is likely related to #4 above.