I purchased a FT232R adapter which claimed to use an FTDI chipset, indeed the seller’s pics showed an FTDI label.
Above, the labelled chip in the seller’s pics. Continue reading Counterfeit FTDI – another form
The first seven days of Exetel broadband Internet access
We have had wired broadband service delivered to these premises for almost ten years, supplied by three vendors: Telstra Bigpond, iiNet, Amaysim, Southern Phone and now Exetel.
The change from Amaysim was at Amaysim’s choice, they decided to quit the wired broadband business stating that they could not make a profit, and they sold their customer base to Southern Phone.
Southern Phone was unable to deliver the VOIP service we have had for many years through all of those broadband suppliers, so we churned to an Exetel “Standard Plus” service.
Cutover
The cutover was badly coordinated, there was a 12 hour outage, and I had to phone Exetel (yes, wait in the interminable queue to try to get the modem PPP credentials, it had DSL service and was routed to Exetel, just needed the authorisation details for Exetel).
Telecommunications providers are all about strong procedures for handling usual business, and this part of the business is known as provisioning. The events with Exetel hint that their provisioning processes are not sensitive to churning an existing NBN connected service which should be done to minimise disruption, including advising the logon credentials, doing it when their support desk is open, holding if the customer needs a new modem etc. This is the bread and butter of the business, but a FAIL to Exetel on this occasion.
First impressions are lasting ones… so how do they come back from that start?
Service levels
I have an expectation that “I want it to deliver most of the rated speed, most of the time during the hours that I want to use it”.
As a result of behaviour of the industry, the ACCC gives some guidance on terms used to advertise a service, and a service expectation.
Essentially they say:
Standard Plus Evening Speed—plans using this label will deliver a minimum speed of 30Mbps during the busy period. This plan would be suitable for a higher usage profile (e.g. streaming an ultra-high definition movie and streaming music on one or more other device during the busy period)
So on that measure, how well did they perform?
Above are the results of file transfer tests conducted automatically, the above are filtered for those in the ACCC’s defined “evening hours” on which they base their service level enforcement. All + symbols in the pink area break the 30Mb/s minimum. Continue reading The first seven days of Exetel broadband Internet access
ISP adapter for Arduino Pro Micro
I have started using Arduino Pro Micros recently, and sourced inexpensive clones from China.
Experience is that all manner of inexpensive small microcontroller modules from China are likely to have issues with the bootloader: it isn’t there, it is back level, not suited to the actual clock speed.
I have come to routinely install a current / known / working bootloader to avoid wasting time down the track.
The Pro Micro does not have an ISP header, and the QFN package does not suit a chip adapter, so the next option is an adapter that can connect to the board with no pins, male or female headers, top or bottom.
Above is an adapter built on a small piece of Veroboard. If you are ging to copy it, make it one row of holes higher. I did initially, and in a miscount of rows, I incorrectly removed the top row. The black mark identifies the USB end of the Pro Micro, and the adapter connects to the side with the /RST pin. Continue reading ISP adapter for Arduino Pro Micro
Yet another change of Internet broadband access
We have had wired broadband service delivered to these premises for almost ten years, supplied by three vendors: Telstra Bigpond, iiNet, Amaysim, Southern Phone and now Exetel.
Download speed
Download speed is an important performance characteristic, and fairly quantifying it is a challenge.
If I were to express my service expectation as “I want it to deliver most of the rated speed, most of the time during the hours that I want to use it” we can express that by better defining the three terms:
- most of the rated speed;
- most of the time; and
- the hours that I want to use it.
Most of the rated speed
Let’s consider that most means 80%, so the critical value of speed is 80% of the rated speed, eg 80% of 12Mb/s is 9.6Mb/s.
Most of the time
Let’s consider that most means 80%, so the critical value is 80% of the time.
During the hours that I want to use it
I sleep at nights, and use the Internet variously during the day, the most important times for service to be adequate are from 06:00 to 20:00.
Critical speed requirement
Capturing the foregoing, I could write “Download speed must exceed 80% of the rated speed, 80% of the time between the hours of 06:00 and 20:00” each week.
This is known as a Service Level specification.
Statistically, this is stated as the 20 percentile speed measured between 06:00 and 22:00 over a week must be greater than 80% of the rated speed.
Test results
A realistic simple HTTP download is scheduled every half hour, and the effective download speed is recorded. This data has been gathered for many years.
Over the nearly 10 years of service, the rated speed has varied, 8, 12, and 50Mb/s at different times. To compare these, the speed in any one observation needs to be normalised to the applicable rated speed, so for this purpose speed is calculated as a percentage of the applicable rated speed.
Telstra
Above is a plot of the measured speed over a period of many years. Continue reading Yet another change of Internet broadband access
IoT – exploration of LoRa – part 3
This series documents a set of experiments to explore LoRa for a telemetry application. Note this is simple multipoint to point LoRa, it does not use LoRaWAN.
IoT – exploration of LoRa – part 1 outlined a simple direct RESTful submission to Thingspeak from the LoRa – Wifi gateway.
IoT – exploration of LoRa – part 2 outlined a simple RESTful submission to Node-Red from the LoRa – Wifi gateway.
This article describes a direct MQTT submission from the gateway. In this case the gateway converts the binary LoRa payload into more friendly MQTT key,value pairs.
The block diagram above shows the information flow between the main elements. Continue reading IoT – exploration of LoRa – part 3
IoT – exploration of LoRa – part 2
This series documents a set of experiments to explore LoRa for a telemetry application. Note this is simple multipoint to point LoRa, it does not use LoRaWAN.
IoT – exploration of LoRa – part 1 outlined a simple direct RESTful submission to Thingspeak from the LoRa – Wifi gateway.
This article introduces an intermediate flexible and extensible Node-Red flow.
The block diagram above shows the information flow between the main elements. Continue reading IoT – exploration of LoRa – part 2
IoT – exploration of LoRa – part 1
This series documents a set of experiments to explore LoRa for a telemetry application. Note this is simple multipoint to point LoRa, it does not use LoRaWAN.
The block diagram above shows the information flow between the main elements. Continue reading IoT – exploration of LoRa – part 1
RFPM2 – calibration files
The RF Power Meter 2 (RFPM2) stores calibration constants in a file located in the (SPIFFS) file system in the microcontroller flash.
The file opened by default when RFPM2 starts is /default.cfg, the following is an example.
{
"name":"dBm",
"hostname":"rfpm201",
"vref":3.3,
"avg":3,
"slope":0.12991,
"intercept":-91.406,
"unit":"dBm",
"lcdfsd":16
}
The parameters above capture the most basic operation of RFPM2 as a power meter directly displaying dBm with bar graph in fixed 2dB increments to 16dBm FSD. These values serve as a basis for some other applications as they capture the basic intercept and slope of the AD8307 module in this instance.
Current probe calibration
Alternative config files can be loaded on the fly from the webserver interface, for example http://192.168.0.86/config?filename=/dBA.cfg will load the dBA config file for a certain current probe. Continue reading RFPM2 – calibration files
RFPM2 – calibration
The RF Power Meter 2 (RFPM2) stores calibration constants in a file located in the (SPIFFS) file system in the microcontroller flash.
The WiFi credentials are stored separately at the default location in the flash.
Calibration constants
The AD8307 outputs a voltage from zero to about 3V for inputs from around -90 to +15dBm. The nominal output has a slope of 25mV/dB and intercept of -84dBm.
A starting point for RFPM2 calibration constants is intercept=-84 and slope=0.129.
Modules such as that used here may have pots to adjust the gain and offset of the output. Adjust the gain so that the maximum output voltage is a little lower than 3.3V (the maximum ADC input), say 2.7V.
The response of the AD8397 has some ripple in the transition between log amp stages. The log cell ranges are 14.3dB, so min error repeats every 14.3dB. My own practice is to calibrate at -62 and -5dBm input as they fall approximately on the mid line of the ripple trend (4 cycles of the error curve). Continue reading RFPM2 – calibration
RFPM2 – current probe
This article describes a current probe for use with a power meter calibrated in dBm (eg RFPM1 and RFPM2).
For use with RFPM1 and RFPM2, both of which read to 16dBm max, it is convenient that the scaling factor for the probe is 0dBA/dBm, ie that those meters read dBA directly, implying a current range of -75-16dBA or 0.186mA-6.3A.
The probe comprises a ferrite cored transformer that is clamped or placed over the conductor(s) of interest, and uses a 10t secondary which has a low value resistive load, across which the power meter connects.
Above is a screen shot of a spreadsheet calculation of relevant design values. Continue reading RFPM2 – current probe