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#91
General topics / Re: Dropped Packets with High ...
Last post by Aerokeith - July 04, 2025, 12:33:55 AMFelix,
I ran a new test with a different method, and this time found that dropping back to the default bitrate considerably reduced the packet drop rate. The drop rate is also reduced if the transmitter and receiver are move further apart (they were only inches apart originally).
At the default bitrate, I see an effective data throughput of about 57 Kbps. Unfortunately, this is a bit too slow for my application, which needs about 70 Kbps. Can you please tell me how to adjust the rate? I searched through the forum but couldn't find a clear answer.
I haven't yet had time to run a test to see if interference from the MCU is the culprit.
Thanks, Keith
I ran a new test with a different method, and this time found that dropping back to the default bitrate considerably reduced the packet drop rate. The drop rate is also reduced if the transmitter and receiver are move further apart (they were only inches apart originally).
At the default bitrate, I see an effective data throughput of about 57 Kbps. Unfortunately, this is a bit too slow for my application, which needs about 70 Kbps. Can you please tell me how to adjust the rate? I searched through the forum but couldn't find a clear answer.
I haven't yet had time to run a test to see if interference from the MCU is the culprit.
Thanks, Keith
#92
General topics / Re: Dropped Packets with High ...
Last post by Aerokeith - July 02, 2025, 08:44:44 PMQuotethe receiver should be in receive mode, that's accomplished by calling receiveDone() and not doing something else in between.Yes, that's what I'm doing.
By "slowly" I mean that I'm sending packets [calling send() ] at a low rate of only a few times a second. I haven't yet found a way to determine if the transmitter is ready to send another packet, so I'm relying on fixed timing.
Quotewhich you maxed out at 300kbps.I commented out the call to set300KBPS() on both the sender and receiver side but that didn't make a difference.
Yes, I understand basic debugging techniques. I'm just looking for additional variables to try.
#93
General topics / Re: Dropped Packets with High ...
Last post by Felix - July 02, 2025, 08:34:43 PMThe receiver should be in receive mode, that's accomplished by calling receiveDone() and not doing something else in between.
When you say slowly, you must mean frequency, not data rate - which you maxed out at 300kbps. Hence, I suggest taking different approaches to change variables in the equation and observe when the behavior stops or changes, then you're close to the problem.
When you say slowly, you must mean frequency, not data rate - which you maxed out at 300kbps. Hence, I suggest taking different approaches to change variables in the equation and observe when the behavior stops or changes, then you're close to the problem.
#94
General topics / Re: Dropped Packets with High ...
Last post by Aerokeith - July 02, 2025, 07:03:10 PMI tried dropping back to the default data rate, but no change in the behavior.
As for #2, I can try testing with my original prototype, which has much greater spacing between the Teensy MCU and the radio module.
But I don't have a spectrum analyzer. In any case, I'm in a pretty rural area. By the way, I check the RSSI on the transmitter side right before each packet is transmitted, and it's a steady -128dBm.
It's just so odd that it's always one packet dropped, never two in a row.
As for #2, I can try testing with my original prototype, which has much greater spacing between the Teensy MCU and the radio module.
But I don't have a spectrum analyzer. In any case, I'm in a pretty rural area. By the way, I check the RSSI on the transmitter side right before each packet is transmitted, and it's a steady -128dBm.
It's just so odd that it's always one packet dropped, never two in a row.
#95
General topics / Re: Dropped Packets with High ...
Last post by Felix - July 02, 2025, 04:15:39 PMCircuit wise, if all is good, and it looks like you know what you're doing, there are 3 things I'd explore to try to narrow this down:
- Unless your application requires so for some very specific reason, I would drop back from 300kbps to the library default. And see if the same behavior persists.
- Number 2 is the obvious elephant in the room, which runs at some insane speeds for such a small micro board. If you have the ability, to try one with another board,
- Analyze the spectrum with a freeze feature to capture sporadic fast packets or used frequencies that might be near or on top of your channel. It's rare, and usually more in a dense urban or industrial setting that stray frequencies jam your own traffic, and perhaps that could be the case.
- Unless your application requires so for some very specific reason, I would drop back from 300kbps to the library default. And see if the same behavior persists.
- Number 2 is the obvious elephant in the room, which runs at some insane speeds for such a small micro board. If you have the ability, to try one with another board,
- Analyze the spectrum with a freeze feature to capture sporadic fast packets or used frequencies that might be near or on top of your channel. It's rare, and usually more in a dense urban or industrial setting that stray frequencies jam your own traffic, and perhaps that could be the case.
#96
General topics / Dropped Packets with High RSSI
Last post by Aerokeith - July 02, 2025, 02:06:45 AMI've been testing some new PCBs that use Sparkfun RFM69HCW modules, and am seeing some strange behavior. I have a single transmitter sending 61 byte packets at a very low fixed rate, between 1 and 10 pkts/sec. The single receiver (eventually will be 4) is receiving most packets correctly, with a RSSI of -31dBm when the boards are close together. But every 5-30 packets or so, one (and only one) packet is entirely dropped. I'm measuring the time between received packets to confirm that it's a single packet drop. The packet drop rate doesn't seem to depend on the receiver RSSI (distance).
Configuration:
Teensy 4.0 MCU (SPI CS on pin 10; Interrupt on pin 2)
Both the transmitter and receiver call setCS(10); setHighPower(); and set300KBPS();
I can't tell if the issue is on the transmitter or receiver side. Since I'm sending packets so slowly, I assume I'm not overrunning the transmit rate, although I don't know how to check that the transmitter is ready (apparently it's not canSend()), or if the send() operation has successfully completed (
).
On the receiver side I'm using receiveDone() to check for packet receipt, and then I read the RSSI immediately afterwards to confirm that it looks good.
Can anyone suggest additional tests to help isolate the issue? Thanks!
Configuration:
Teensy 4.0 MCU (SPI CS on pin 10; Interrupt on pin 2)
Both the transmitter and receiver call setCS(10); setHighPower(); and set300KBPS();
I can't tell if the issue is on the transmitter or receiver side. Since I'm sending packets so slowly, I assume I'm not overrunning the transmit rate, although I don't know how to check that the transmitter is ready (apparently it's not canSend()), or if the send() operation has successfully completed (
). On the receiver side I'm using receiveDone() to check for packet receipt, and then I read the RSSI immediately afterwards to confirm that it looks good.
Can anyone suggest additional tests to help isolate the issue? Thanks!
#97
RF - Range - Antennas - RFM69 library / Re: Antenna Advice?
Last post by Felix - June 17, 2025, 03:50:31 PMIt should be just fine. I'd be surprised if 3 wheels receivers work well and 1 doesn't at all.
#98
RF - Range - Antennas - RFM69 library / Re: Antenna Advice?
Last post by Aerokeith - June 13, 2025, 04:30:18 PMThere's a lot of metal and with a single antenna, no direct line of sight to all four wheels. Will reflected signals work well enough? I'll be able to test in a couple of weeks, but I'm thinking about options in case it doesn't go well.
#99
RF - Range - Antennas - RFM69 library / Re: Antenna Advice?
Last post by Felix - June 13, 2025, 10:50:31 AMA single antenna will be just fine. Any antenna for that matter. The range is negligible.
#100
RF - Range - Antennas - RFM69 library / Antenna Advice?
Last post by Aerokeith - June 12, 2025, 04:22:42 PMI'm using a RFM69HCW module (https://www.sparkfun.com/rfm69hcw-wireless-transceiver-915mhz.html) to transmit data at ~60 Kbps to the wheel hubs of a large vehicle. I'd like to use an off-the-shelf outdoor antenna like this one (https://www.amazon.com/Network-AOA-915-5ACM-Outdoor-802-11ah-Application/dp/B08H8J6ZV6/)
on each wheel and the body. Any better suggestions?
I'm concerned that a single body-mounted antenna won't have good enough line-of-sight to all four wheels, so I'm considering an antenna on each side of the vehicle. Is there a way I can use two antenna with a single transmitter? If I need to use a separate transmitter for each antenna, how much frequency separation do I need to avoid. interference?
Thank you!
on each wheel and the body. Any better suggestions?
I'm concerned that a single body-mounted antenna won't have good enough line-of-sight to all four wheels, so I'm considering an antenna on each side of the vehicle. Is there a way I can use two antenna with a single transmitter? If I need to use a separate transmitter for each antenna, how much frequency separation do I need to avoid. interference?
Thank you!