SPI and ItsyBitsy M4

General Discussion
1

Hi, the atsamd51/21 MCU’s need to have sercom configured for SPI. I’m trying to setup a itsybitsy M4 (atsam51) with Klipper.

If I configured the SPI per what I’m fairly sure is the correct config for this board I get ‘Invalid SERCOM configuration’.

sercom: sercom1
tx_pin: samd:PA0 #MOSI
rx_pin: samd:PB23 #MISO
clk_pin: samd:PA1 #CLK

Reading the source in src/atsamd/sercom.c, I see that for sercom1 PB23 is not allows (this is actually allowed, as the MISO pin can be on any valid pad on the atsam51.

So I changed the pins to a valid set, as below but I still get the same error.
sercom: sercom1
tx_pin: samd:PA0 #MOSI
rx_pin: samd:PA31 #MISO (have tried PA30 also)
clk_pin: samd:PA1 #CLK

If I use the following I do not get an error
sercom: sercom0
tx_pin: samd:PA4 #MOSI
rx_pin: samd:PA7 #MISO
clk_pin: samd:PA5 #CLK

The SPI does not work because these pins are incorrect for the board but at least the errors stopped.

At this point I decided I need to check if the data was getting to the function which was causing the message and shutdown.
I changed sercom_lookup_pad to the following

static const struct sercom_pad *
sercom_lookup_pad(uint32_t sercom_id, uint8_t pin)
{
    const struct sercom_pad *sp = sercom_pads;
    char strpin[2] = "r";
    uint8_t h = sercom_id % 0xff;
    strpin[0] = h+64;
    output("error: %s", strpin);

    strpin[0] = pin+64;
    output("error: %s", strpin);
    for (; ; sp++) {
        if (sp >= &sercom_pads[ARRAY_SIZE(sercom_pads)]) {

            shutdown("Invalid SERCOM configuration");
        }
        if (sp->sercom_id == sercom_id && sp->gpio == pin)
            return sp;
    }
}

I then tried the working config again

[samd_sercom samd_spi]
sercom: sercom0
tx_pin: samd:PA4 #MOSI
rx_pin: samd:PA7 #MISO
clk_pin: samd:PA5 #CLK

This results in
mcu ‘samd’: #output: error: ‘@’ ← is sercom0
mcu ‘samd’: #output: error: ‘D’
mcu ‘samd’: #output: error: ‘@’
mcu ‘samd’: #output: error: ‘G’
mcu ‘samd’: #output: error: ‘@’
mcu ‘samd’: #output: error: ‘E’

Now I try which is a valid config for sercom1 but still not valid for the board.
sercom: sercom1
tx_pin: samd:PA0 #MOSI
rx_pin: samd:PA31 #MISO (have tried PA30 also)
clk_pin: samd:PA1 #CLK

This results in
Receive: 75 224034.722536 224034.721611 8: seq: 11, #output error: ‘@’ < sercom0 but should be 1
Receive: 76 224034.722558 224034.721611 8: seq: 11, #output error: ‘@’ ← tx_pin

From this I see that the code does not correctly set the sercom to 1 so the table in the source code does not match anything.

Finally the issue is that the table in sercom.c does not allow for the fact that PB23 is a valid pin for MISO.
IE
sercom: sercom1
tx_pin: samd:PA0 #MOSI
rx_pin: samd:PB23 #MISO
clk_pin: samd:PA1 #CLK

As a result I think there is a bug which is not correctly processing the sercom port and then there is an issue with the allowed pins in the table.

klipper_m4_bad_goodline.zip (29.1 KB)
klipper_m4_ok.zip (26.8 KB)

Cheers
Mike

2

Last example log file
klipper_m4_good_config.zip (28.8 KB)

3

FWIW, I don’t understand what you are reporting here - you have too many different possible configs for me to follow along.

If you can have a single hardware config that you think should work, then please attach the full unmodified klipper log running unmodified klipper code with that config, and I’ll try to take a look at it. It is important the log and code both have no modifications - as otherwise it is too time consuming for me to investigate it.

Cheers,
-Kevin

4

Ok, simply put there is a bug in the sercom code which does not allow me to use the board with SPI.

I’ll give you a log matching the boards requirements.

Mike

5

Clean, current head code build and flashed to the M4 (still using older firmware on the printer and linux mcu)
klipper_log.zip (28.7 KB)

Cheers
Mike

6

I just found another document that confirms my general config.

7

Alas, that log is not complete. I need the full, unmodified, log or otherwise it is just too time consuming for me.

-Kevin

8

I do not understand now it could not be complete. I cleared the log restarted klipper waited until it shutdown and then compressed it and uploaded it
I’ll try again.

9

klipper_log_0645.zip (39.2 KB)

10

Was this log any good?

11

Ah, you didn’t actually specify the sercom bus to use. It should be something like:

[adxl345]
cs_pin: samd:PA16
spi_bus: sercom1

I cleared the log restarted klipper waited until it shutdown and then compressed it and uploaded it

The latest log was complete (it had the necessary version information at the top of the log). I’m not sure how the incomplete logs were generated. For future reference, make sure you don’t “clear the log” while Klipper is running - if you want to start from a fresh log, stop Klipper with sudo service klipper stop, then remove the logs rm /tmp/klippy.log*, and then restart sudo service klipper start.

-Kevin

12

That extra setting fix the start error but its not working. That could be my wiring so I’ll spend some time checking it before opening a new topic.