Frequently Asked Questions
The JTAG/J-Link adapter board follows the Segger pinouts:
20-pin - https://www.segger.com/products/debug-probes/j-link/technology/interface-description/
10-pin - https://www.segger.com/products/debug-probes/j-link/models/j-link-edu-mini/
Note on the 20-pin adapter board header, the DBGRQ pin is not connected (it is not connected inside the J-Link programmer anyway). The VCC control pin from the Port MuxR is connected to the 5V-Supply pin, so you also need to set the supply voltage switch on the Port MuxR as appropriate.
It may work for other similar JTAG pinouts, however you need to make sure the appropriate pins will be available on your device and programmer (notably DBGRQ and DGBACK pins).
As for AVR adapter board, it follows the standard AVR 6 and 10 pin ICSP interface - https://cdn.sparkfun.com/assets/d/8/9/c/9/527158c7757b7f17048b4567.pngLast updated:
The port MuxR isn't really designed for use with negative voltages. However, lower peak to peak voltage AC signals do pass through the FET switches just fine when the port is on. There is a big caveat though, the signal may clip and distort when it gets below -2 volts.
For a bit of a technical explanation, negative voltage flowing to the other FET switches that are off, can inadvertently switch them on. This is due to the FET's gate voltage being at ground potential and the input voltage being greater than the NMOS threshold voltage, which causes it to conduct and activate the pin. The -2V undershoot protection counteracts this by tracking the gate to the input voltage down to -2V, to keep it from being greater than the threshold voltage up until this point.
The best solution is to create an adapter board, to DC offset/bias the signal and allow it through the MuxR. Then you can just put the signal through a series capacitor to remove the the DC offset on the other side of the MuxR. Just make sure the peak to peak voltage is below 5V and the offset doesn't bring the peak much over 5V.Last updated:
This is a slightly tricky question to answer as there are many factors that determine the maximum bandwidth a circuit can support. The FET switches themselves are not actively switching on and off like a transistor does, they act more like an RC filter (their on state resistance and capacitance determine the frequency cutoff). Different cabling, connectors, lengths and type of signal also play a role in the way a circuit performs.
The FETs on board have a typical RC time constant of 0.15ns, which is calculated from its typical on state resistance (3 ohm @ 3V) and typical load capacitance with connectors and cables (50pF) from an ideal voltage source (zero output impedance). This equates to a signal bandwidth of about 1GHz (this value will increase or decrease depending on the total circuit characteristics). However, crosstalk effects will also play a role in how stable your signal is. The boards themselves are 4-layer PCBs with a grounding plane which helps reduce these crosstalk effects between signalling lines.
We have tested the boards with 50MHz square wave/clock signals from a signal generator (rule of thumb around ~200MHz bandwidth) with few ill effects to the signal. So to play it safe, all clock signals under 50MHz should work perfectly fine (provided your cabling and additional circuitry supports this), which covers most embedded system use cases. Higher bandwidth signals should work fine too, but signals that are crosstalk and attenuation resistant, such as differential signals, will yield better results.Last updated:
Of course you can!
If you are looking for a specific combination of adapter boards, just select the number of Port MuxR's you prefer, then add an additional $40AUD per adapter board style you require to the pledge amount.
If you would like more than 4x Port MuxR's, please get in touch first and we can work out a price for you to pledge.
We will confirm reward preferences with backers that have put in additional amounts at the end of the campaign.Last updated:
MuxR is pronounced mux'er, the short form of multiplexer. The R stands for remixed, as in it is a reworked version of the original port switcher we developed.Last updated:
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