Hello,
I have been investigating.
with debug gdb, I was able to get the tx_buffer. I don't understand why it
does not transmit all the buffer. It is like the Block Transfer Counter
(btcnt) is not
calculated properly or something similar which truncate the buffer.
0x60 is ONE
0x78 is ZERO
0x0 is RESET
x/45 txbuffer
0x200023c8: 0x0 0x0 0x0 0x0
0x200023d8: 0x0 0x0 0x0 0x0
0x200023e8: 0x0 0x0 0x0 0x0
0x200023f8: 0x0 0x0 0x0 0x60606060
0x20002408: 0x60606060 0x60606060 0x60606060 0x60606060
0x20002418: 0x60606060 0x60606060 0x60606060 0x60606060
0x20002428: 0x60606060 0x60606060 0x60606060 0x60606060
0x20002438: 0x60606060 0x60606060 0x60606060 0x60606060
0x20002448: 0x60606060 0x60606060 0x60606060 0x60606060
0x20002458: 0x60606060 0x60606060 0x60606060 0x60606060
0x20002468: 0x60606060 0x60606060 0x60606060 0x60606060
0x20002478: 0x60606060
The syslog gives me:
Start: 0 End: 4
txbuffer=0x200023c8 rxbuffer=0 nwords=181
#define TXBUFF_SIZE(n) (WS2812_RST_CYCLES + n * WS2812_BYTES_PER_LED + 1)
TXBUFF_SIZE(5 leds) = 60 + 5 * 24 + 1 = 181 which correspond to the buffer
size: 45 * 4 + 1 = 181.
Other thing. I dig in the register definitions (sam_dmac.h, sam_spi.h) and
sometime I find the _MASK values to be on Reserved bits of the register.
when those are redefined elsewhere I can understand but for example this
one is on reserved bit and never redefined:
#define DMACH_FLAG_BEATSIZE_MASK (3 << DMACH_FLAG_BEATSIZE_SHIFT)
BEATSIZE can be 0,1 or 2. Why 3? I set it up to 2 manually.
Regards,
Bert.
Le mar. 31 oct. 2023 à 23:27, Bert Voldenuit <bertvolden...@gmail.com> a
écrit :
> Hello Alan,
>
> It is better with DMA. I think there is an error in sam_dmac.c line 140 I
> had to change aligned to aligned_data, otherwise I get
> error: expected declaration specifiers or '...' before numeric constant
>
> static struct dma_desc_s g_base_desc[SAMD2L2_NDMACHAN]
> locate_data(".lpram"), aligned(16);
> static struct dma_desc_s g_writeback_desc[SAMD2L2_NDMACHAN]
> locate_data(".lpram"), aligned(16);
> to
> static struct dma_desc_s g_base_desc[SAMD2L2_NDMACHAN]
> locate_data(".lpram") aligned_data(16);
> static struct dma_desc_s g_writeback_desc[SAMD2L2_NDMACHAN]
> locate_data(".lpram") aligned_data(16);
>
> Still in the same file, changed the configuration of the Channel Control B
> Reg.
> Instead of DMAC_CHCTRLB_TRIGACT_BEAT by DMAC_CHCTRLB_TRIGACT_TRANSACT it
> works also with DMAC_CHCTRLB_TRIGACT_BLOCK.
>
> With DMAC_CHCTRLB_TRIGACT_BEAT I get only one pulse every 20ms
> (application delay)
>
> With DMAC_CHCTRLB_TRIGACT_TRANSACT or DMAC_CHCTRLB_TRIGACT_BLOCK I get:
> - a reset >80µs
> - 13 bits. The bits are packed. However I think it should be 24bits. Maybe
> I saturate the DMA because of the reset which take many bytes??
> - Led 1 is turning on and off but with green color only
>
> [image: dso_01_01_02_59_38.png]
> Regards,
> Bert.
>
> Le lun. 30 oct. 2023 à 18:57, Alan C. Assis <acas...@gmail.com> a écrit :
>
>> Hi Bert,
>>
>> On 10/30/23, Bert Voldenuit <bertvolden...@gmail.com> wrote:
>> > Hi Alan,
>> > Thanks for adding Brennan to the discussion.
>> >
>> > My answers below.
>> >
>> > Le lun. 30 oct. 2023 à 16:09, Alan C. Assis <acas...@gmail.com> a
>> écrit :
>> >
>> >> Hi Bert,
>> >>
>> >> I'm CC Brennan (the original author) and Victor (the author of the
>> >> other driver using ESP32 RMT) they have more experience with WS2812.
>> >>
>> >> On 10/29/23, Bert Voldenuit <bertvolden...@gmail.com> wrote:
>> >> > Hi Alan,
>> >> >
>> >> > Thanks to your advices, I was able to find why
>> >> > board_ws2812_initialize()
>> >> > was not in System.map.
>> >> > Now it mounts and opens ws2812 driver.
>> >> >
>> >>
>> >> Great, what was the issue?
>> >
>> > --> I forgot to activate board_late_initialized
>> > --> By default the ws2812 driver allocate memory for each color (8bits)
>> for
>> > RGBW (4 colors). My leds are RGB only so I had to change 4->3. I will
>> try
>> > to add a parameter instead of a fixed value.
>> >
>> >>
>> >> > Indeed the SPI is not a piece of cake. I think I have it almost right
>> >> > but
>> >> > MOSI pin is idling high which is a problem for the reset which must
>> be
>> >> low
>> >> > and I can' get it to the right timing.
>> >> >
>> >>
>> >> Exactly, using SPI to control the WS2812 seems challenging, you will
>> >> need to fiddling with it a little bit until get things working.
>> >>
>> >> > SPI frequency is set to 6MHz
>> >> >
>> >> > In ws2812.c
>> >> > I had to change WS2812_ONE_BYTE. I added one more 1 to fit the timing
>> >> > for
>> >> > SK6812
>> >> > Target Measured (see Scope figure 1)
>> >> > T0H 0 0.3μs ±0.15μs 0.34µs
>> >> > T1H 1 0.6μs ±0.15μs 0.68µs
>> >> > T0L 0 0.9μs ±0.15μs 0.86µs
>> >> > T1L 1 0.6μs ±0.15μs 0.52µs
>> >> > Reset 80µs 20µs (Not Good)
>> >> >
>> >>
>> >> I'm not sure you need to change the number of bits, AFAIK it should be
>> >> only the frequency you should play with. SAMD21 (and many others SAM
>> >> chips) has a very advanced clock system (even compared with some
>> >> advanced processor)
>> >>
>> > --> True! I will try to fit the target by changing the clock without
>> > changing the bits
>> >
>> >
>> >> > I Changed WS2812_RST_CYCLES for 80µs but I still get 20µs, so it look
>> >> like
>> >> > it has no effect AND it is idling High (see Scope figure 2).
>> >> >
>> >> > Questions:
>> >> >
>> >> > - On Scope Figure 1, is it normal SPI is idling for 2.2µs between
>> each
>> >> > byte?
>> >> >
>> >>
>> >> It could be caused by the driver itself. Maybe using SPI with DMA will
>> >> reduce this idle time.
>> >
>> > --> Ah! I thought it was already using DMA. Now I understand that the
>> delay
>> > should be the cpu time needed to send the next bit.
>> > --> Yes using the DMA would definitely improve the driver. I checked on
>> > another library that it is possible to loop on DMA so when there is no
>> data
>> > to send, it sends zeros forever at no cpu cost.
>> > --> I have no idea how to handle and allocate DMA. I saw a DMA trigger
>> in
>> > the SPI option, will it be necessary to activate? I will try to add the
>> DMA
>> > option in the driver.
>> >
>>
>> The SPI driver already supports DMA, you just need to use
>> CONFIG_SAMD2L2_SPI_DMA
>>
>> BR,
>>
>> Alan
>>
>
