From 13620cc4db2c3e0d2655c6ee7ad9faab934488e2 Mon Sep 17 00:00:00 2001 From: Jeff Epler Date: Mon, 9 Dec 2019 10:57:55 -0600 Subject: nRF: PWMAudioOut: fix half-speed playback of stereo samples The "spacing" of "buffer structure" is confusing, use the "channel count" instead. Testing performed on nrf52840 feather: Play stereo and mono, 8- and 16-bit, 8kHz RawSamples representing 333.33Hz square waves. Use both mono and stereo PWMAudioOut instances. Scope the RC-filtered signal and use the scope's frequency measurement function, verify the frequency is 333 or 334Hz in all tested cases. In the "stereo output" cases, verify both the L and R channels. Verify the output amplitude is the same in both channels. In the "stereo output" cases, run a second test where the L channel's amplitude is attenuated 50%. Verify the output amplitude is correct in each channel. --- ports/nrf/common-hal/audiopwmio/PWMAudioOut.c | 16 ++++++++++------ ports/nrf/common-hal/audiopwmio/PWMAudioOut.h | 2 +- 2 files changed, 11 insertions(+), 7 deletions(-) diff --git a/ports/nrf/common-hal/audiopwmio/PWMAudioOut.c b/ports/nrf/common-hal/audiopwmio/PWMAudioOut.c index 9496277b1..b4c626355 100644 --- a/ports/nrf/common-hal/audiopwmio/PWMAudioOut.c +++ b/ports/nrf/common-hal/audiopwmio/PWMAudioOut.c @@ -97,27 +97,28 @@ STATIC void fill_buffers(audiopwmio_pwmaudioout_obj_t *self, int buf) { common_hal_audiopwmio_pwmaudioout_stop(self); return; } - uint32_t num_samples = buffer_length / self->bytes_per_sample / self->spacing; + uint32_t num_samples = buffer_length / self->bytes_per_sample / self->sample_channel_count; + uint16_t *end_dev_buffer = dev_buffer + 2 * num_samples; if (self->bytes_per_sample == 1) { uint8_t offset = self->signed_to_unsigned ? 0x80 : 0; uint16_t scale = self->scale; - for (uint32_t i=0; ispacing; i++) { + while (dev_buffer < end_dev_buffer) { uint8_t rawval = (*buffer++ + offset); uint16_t val = (uint16_t)(((uint32_t)rawval * (uint32_t)scale) >> 8); *dev_buffer++ = val; - if (self->spacing == 1) + if (self->sample_channel_count == 1) *dev_buffer++ = val; } } else { uint16_t offset = self->signed_to_unsigned ? 0x8000 : 0; uint16_t scale = self->scale; uint16_t *buffer16 = (uint16_t*)buffer; - for (uint32_t i=0; ispacing; i++) { + while (dev_buffer < end_dev_buffer) { uint16_t rawval = (*buffer16++ + offset); uint16_t val = (uint16_t)((rawval * (uint32_t)scale) >> 16); *dev_buffer++ = val; - if (self->spacing == 1) + if (self->sample_channel_count == 1) *dev_buffer++ = val; } } @@ -231,9 +232,12 @@ void common_hal_audiopwmio_pwmaudioout_play(audiopwmio_pwmaudioout_obj_t* self, self->bytes_per_sample = audiosample_bits_per_sample(sample) / 8; uint32_t max_buffer_length; + uint8_t spacing; audiosample_get_buffer_structure(sample, /* single channel */ false, &self->single_buffer, &self->signed_to_unsigned, &max_buffer_length, - &self->spacing); + &spacing); + self->sample_channel_count = audiosample_channel_count(sample); + if (max_buffer_length > UINT16_MAX) { mp_raise_ValueError_varg(translate("Buffer length %d too big. It must be less than %d"), max_buffer_length, UINT16_MAX); } diff --git a/ports/nrf/common-hal/audiopwmio/PWMAudioOut.h b/ports/nrf/common-hal/audiopwmio/PWMAudioOut.h index 8deff5d34..ed00324c4 100644 --- a/ports/nrf/common-hal/audiopwmio/PWMAudioOut.h +++ b/ports/nrf/common-hal/audiopwmio/PWMAudioOut.h @@ -41,7 +41,7 @@ typedef struct { uint8_t left_channel_number; uint8_t right_channel_number; - uint8_t spacing; + uint8_t sample_channel_count; uint8_t bytes_per_sample; bool playing; -- cgit v1.2.3