Is there a way to have 6 different GPIOs act in unison off one event/action? I need all 6 to go ON and OFF at EXACTLY the same time based of an event or action.
Is there a way to have 6 different GPIOs act in unison off one event/action? I need all 6 to go ON and OFF at EXACTLY the same time based of an event or action.
Torbjørn, is there a way to do this from a PWM? For example have one channel trip 6 outputs?
Hi Brian
You can't have a single PWM channel trigger 6 outputs, but it is pretty straight forward to set up 6 individual PWM channels to trigger at the same time.
You don't mention which nRF52 device you are interested in, but the nRF52832 has 12 PWM channels in total, while the nRF52840 has 16.
You could also use 6 of the 8 GPIOTE channels to trigger 6 pins in unison, but I think the PWM is a better choice since each PWM module can handle up to 4 channels easily (with the GPIOTE you would have to fire off 6 events at the same time, versus just 2 for the PWM solution).
Best regards
Torbjørn
Torbjørn - The hardware designer connected 6 I/O pins together to try and increase the drive capability. The 6 I/O need to be driven by the PWM. Currently I have one PWM driving 4 channels (4 of the outputs), and I have the other two I/O set as disconnected inputs. I wanted to make sure all of the pins switch at the same time which is why I used only one PWM (all 4 outputs work off same clock). I would think the outputs need to switch together to avoid shorting the supply. Thanks for the help!
I am using the nRF52832
Hi Brian
How much drive current do you need?
I am not sure how efficient this method will be in increasing the maximum current, as there is a limit on how much you can draw from all the pins put together, limited by the regulators in the chip.
This limit is highly dependent on supply voltage, with a higher supply voltage allowing you to draw a higher current from the pins.
Best regards
Torbjørn
Torbjørn - we are trying to drive a single FET that is part of a boost power supply. E.g. 3V battery thru an inductor to the FET to ground. The nRF52832 is driving the FET. We are running a PWM at 400khz. The Nordic doesn't seem able to pull down/up the FET gate fast enough for the circuit to work. Specifically it has a hard time pulling DOWN the gate to turn it OFF. We currently have 4 outputs from the PWM driving the gate. I have them defined as H0S1, which gives the best results, but still not adequate. The input capacitance on the current FET is 262nf. We have a different FET on order with an input capacitance of 32pf. We are hoping that solves the problem.
Torbjørn - we are trying to drive a single FET that is part of a boost power supply. E.g. 3V battery thru an inductor to the FET to ground. The nRF52832 is driving the FET. We are running a PWM at 400khz. The Nordic doesn't seem able to pull down/up the FET gate fast enough for the circuit to work. Specifically it has a hard time pulling DOWN the gate to turn it OFF. We currently have 4 outputs from the PWM driving the gate. I have them defined as H0S1, which gives the best results, but still not adequate. The input capacitance on the current FET is 262nf. We have a different FET on order with an input capacitance of 32pf. We are hoping that solves the problem.
262 nF, sure that's not 262 pF?
When driving FETs with high frequencies like this, the drive current will be relativily high since you have to charge and discharge the gate capacitance very fast. A better way is to use a smaller FET to drive the larger one and make sure you don't have any resistance in series with the gate.
Yes, sorry pF. As a followup, using the 32pf FET works great. The trade off however is Rdson. We would prefer the higher input capacitance part, so the question still remains how to drive 6 outputs simultaneous. Thanks!
A better way is to use a smaller FET to drive the larger one
Or to use a proper FET driver ...
the question still remains how to drive 6 outputs simultaneous.
I think the real question is, "how to drive the big FET?"
As noted above, trying to parallel 6 GPIOs is not a good answer to that question!