libraries/PDM/src/PDM.cpp: Add PDM begin and end. #160

Rathan25 · 2025-09-18T14:05:24Z

PR Description.

Added PDM.begin(), Which dose initialization of PDM, enables channels, configures sample rate.
Added PDM.end(), which disables PDM and clear the FIFOs.
In example added Basic test on begin() and end().

Done unit test with channels and passing sample rate. For single channel it configures with left channel . Going forward need to check with application

Captured logs:

Signed-off-by: Rathan25 <[email protected]>

ederjc

Please complete the work or open against a feature branch.
Also, make sure the checks are passing.

jaenrig-ifx

Good start 👍
We have to also start thinking of the tests in arduino-core-test
In micropython we have faked a pcm signal with gpio toggling and then read the pattern from the receiver:
https://github.com/Infineon/micropython/blob/ports-psoc6-main/tests/ports/psoc6/board_ext_hw/multi/pdm_pcm_rx.py
https://github.com/Infineon/micropython/blob/ports-psoc6-main/tests/ports/psoc6/board_ext_hw/multi/pdm_pcm_tx.py

jaenrig-ifx · 2025-09-23T07:58:26Z

libraries/PDM/keywords.txt

+# Instances (KEYWORD2)
+#######################################
+
+PDM	KEYWORD2


As we are going to be able to create multiple instances, this should be a data type -> KEYWORD1

jaenrig-ifx · 2025-09-23T08:12:09Z

libraries/PDM/src/PDM.h

+#include "Arduino.h"
+#include "cyhal_pdmpcm.h"
+
+#define PDM_DATA   P10_5


We should create a constructor which accepts the pins, like ->
https://github.com/Infineon/arduino-core-psoc6/blob/main/libraries/Wire/src/Wire.h#L17*
Then we can have a pre-instantiated object like this:
https://github.com/Infineon/arduino-core-psoc6/blob/main/libraries/Wire/src/Wire.cpp#L236-L241
And those defines are part of the pins_arduino.h -> https://github.com/Infineon/arduino-core-psoc6/blob/main/libraries/Wire/src/Wire.cpp#L236-L241

jaenrig-ifx · 2025-09-23T09:57:57Z

libraries/PDM/src/PDM.cpp

+        return; \
+}
+
+bool PdmClass::begin(int channels, int sample_rate) {


As discussed, there are few more things that need to be taken care in the begin:

irq setup

dma

ringbuffer usage (there is a coreAPI ringbuffer that maybe can be used -> https://github.com/arduino/ArduinoCore-API/blob/master/api/RingBuffer.h

The clock also needs to be setup depending on the sampling rate.
https://github.com/Infineon/micropython/blob/ports-psoc6-main/ports/psoc6/machine_pdm_pcm.c#L435-L499
It is fine, you can gradually add that in subsequent PR.

jaenrig-ifx · 2025-09-23T09:59:13Z

libraries/PDM/src/PDM.h

+#define PDM_DATA   P10_5
+#define PDM_CLK    P10_4
+
+#define SAMPLE_RATE_HZ   8000u


These defines can be private, in the .cpp?

jaenrig-ifx · 2025-09-23T10:00:51Z

libraries/PDM/src/PDM.h

+#define SAMPLE_RATE_HZ   8000u
+#define DECIMATION_RATE  64u
+
+class PdmClass {


I would name it PDMClass, as here -> https://github.com/arduino/ArduinoCore-mbed/blob/main/libraries/PDM/src/PDM.h

As per your comments, done changes. ISR is working. Please review once.

commit for fix
082bf15

Signed-off-by: Rathan25 <[email protected]>

jaenrig-ifx

A few comments to work on.
In parallel we should start with the tests.

jaenrig-ifx · 2025-09-25T13:50:21Z

libraries/PDM/src/PDM.h

+    PDMClass(pin_size_t sda, pin_size_t scl);
+    PDMClass(); // Constructor
+
+    int32_t active_rx_buffer[BUFFER_SIZE];


Are these variables required to be public?

jaenrig-ifx · 2025-09-25T13:50:40Z

libraries/PDM/src/PDM.h

+    void end();
+    uint32_t available();
+    uint32_t read(uint16_t *out_buffer, uint32_t samples_to_read);
+    static void pdm_pcm_isr_handler(void *arg, cyhal_pdm_pcm_event_t event);


Is the isr handled required to be public?

jaenrig-ifx · 2025-09-25T14:12:42Z

libraries/PDM/src/PDM.h

+#include "cyhal_pdmpcm.h"
+#include "cyhal.h"
+
+#define SAMPLE_RATE_HZ                      8000u


These defines could be constexpr and private, as they are only relevant to the internal of the class, or?
https://medium.com/@newcreation2kal/const-constexpr-and-macros-in-c-db806ece0b87

jaenrig-ifx · 2025-09-25T14:21:22Z

libraries/PDM/src/PDM.cpp

+    Serial.println("Begin function called");
+
+    if (channels != 1 && channels != 2) {
+        Serial.println("Invalid channel. Desired channel should be 1 0r 2");


We usually do not add Serial.print() calls in the library.
Reasons: they are computationally expensive, can interfere with the application performance, the Serial might not be required or even available by the application...
They can be convenient for debugging as you are using them now (as long as they don´t interfere with the functionality).
So keep them if you still need them, and we can remove them before merging to main.
We could implement them as macros that can be enabled/disabled conditionally. But we have not done that for any other built-in lib.

jaenrig-ifx · 2025-09-25T14:45:29Z

libraries/PDM/src/PDM.cpp

+        return false;
+    }
+
+    cyhal_pdm_pcm_register_callback(&pdm_pcm, pdm_pcm_isr_handler, this);


A bit of encapsulation of each of these calls would help with readability and maintainability.

As here:
https://github.com/Infineon/micropython/blob/ports-psoc6-main/ports/psoc6/machine_pdm_pcm.c#L494-L498

jaenrig-ifx · 2025-09-25T14:46:50Z

libraries/PDM/src/PDM.cpp

+    PDMClass::clock_init();
+    // ringbuf_init -->to be implemented
+
+    cyhal_gpio_init(CYBSP_USER_LED, CYHAL_GPIO_DIR_OUTPUT, CYHAL_GPIO_DRIVE_STRONG, CYBSP_LED_STATE_ON);  // pcm signal with gpio toggling


The gpio toggling is a temporary utility or? We know... but good if we would add a comment for such things

Signed-off-by: Rathan25 <[email protected]>

libraries/PDM/src/PDM.cpp: Add PDM begin and end.

51f639c

Signed-off-by: Rathan25 <[email protected]>

Rathan25 requested review from ederjc, jaenrig-ifx and ramya-subramanyam as code owners September 18, 2025 14:05

ederjc requested changes Sep 19, 2025

View reviewed changes

Rathan25 changed the base branch from main to pdm_integration September 22, 2025 11:39

jaenrig-ifx requested changes Sep 23, 2025

View reviewed changes

libraries/PDM/src/PDM.cpp: Fixes on begin.

082bf15

Signed-off-by: Rathan25 <[email protected]>

Rathan25 requested review from ederjc and jaenrig-ifx September 24, 2025 12:43

libraries/PDM/src/PDM.cpp: Gain, Fixes on begin.

b01b040

Signed-off-by: Rathan25 <[email protected]>

jaenrig-ifx requested changes Sep 25, 2025

View reviewed changes

libraries/PDM/src/PDM.cpp: Add ring buffer.

df3902c

Signed-off-by: Rathan25 <[email protected]>

libraries/PDM/src/PDM.cpp: Add PDM begin and end. #160

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libraries/PDM/src/PDM.cpp: Add PDM begin and end. #160

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Rathan25 commented Sep 18, 2025 •

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Rathan25 Sep 24, 2025 •

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