Pinout from Pulse Out from PDB module

[adamandersson]

Hello. Trying to use the Pulse out on the PDB module to generate a pulse to a PORT. Is it possible to connect the pulseout to any of the PORT:s? Currently using interrupt to generate a pulse but would like to generate a faster and more precice pulse.

[mjbcswitzerland]

Hi

The PDB has a DMA trigger capability (MUX0 source 48).
This can be used to trigger 2 writes to the port toggle register in question to generate a pulse on the pin. If you want, you can trigger a sequence of multiple writes (copies from const table values for example) which generate a longer pulse width or other output sequences.

See this for a similar use of DMA to toggle outputs - the DMA trigger source needs to be set to the PDB instead of a port input: https://community.nxp.com/message/923862?commentID=923862#comment-923862 

Regards

Mark

[adamandersson]

Thank you. Is it not possible to use the Pulse out part of the PDB module (Using the PDBx_POnDLY registers) on a port?

[mjbcswitzerland]

Hi

The pulse out is an internal signal which is connected internally to the CMP module. I don't now of a way to use this to generate outputs on pins.

If you already have an interrupt from the PDB with the required timing you just need to enable DMAEN in PDBx_SC to get the same timing controlling a DMA transfer.

Regards

Mark

[adamandersson]

Hi

Enabling the PDB0 channel pulse out on channel 0 should according to my understanding send the signal to CMP0 and by enabling CMP0 and mimicking the input from the comperator should be able to send out the signal CMP0_OUT to e.g. PTC5 (MUX = 0x6?).

Thank you for your help.

[mjbcswitzerland]

Adam

I checked and agree that if you attach the PDB pulse output to the CMP and set its other input to, say 1.6V (from 6-bit DAC) it should generate a pulse on the CMP out pin (when configured for this peripheral mode). Therefore it is worth trying - please tell us if it works as expected.

Note that I tend to use the DMA method since it allows such things to be done on any output (or multiple outputs), which is especially useful when the HW design has already been completed and it is realised that such a function could be useful (without need to change the board design).

Regards

Mark

[adamandersson]

Might be that the Pulse out part of the PDB is only connected to the sample input of the CMP module and not the reference input. This wording in the description of the PDB module(see picture below) is a bit strange but it seems like i should be possible to use it directly to a package pin or is it that the CMP module is able to be connected to a package pin? I will continue and try using DMA and ADC pre-triggering to generate the pulse instead.

Is there delay issues with using DMA to set or clear ports?

Thanks for helping

Adam