USB issue

[vsurducan]

Hi, I've seen two complete examples of using USB libraries; both are bootloaders, one using 18F4450 and the other 18F14k50.

Both are using USB clocks at 48MHz, so USB runs in full speed mode. Both use an external crystal in HF mode and PLL to acquire 48MHz clock.

The bootloader for 18F4450 works ok also on 18F2550 without any issue...I've tested a while ago.

I'm trying to use usb_serial on a 18F25k50 running in INTOSC mode 48MHz (16Mhz and 3x PLL) and USB module in low speed mode (6MHz).  The computer does not read OK the USB device descriptor when the PIC is connected. This can be a communication issue but also a software error.

Anyone know if full speed is mandatory for these USB libraries?

Maybe there is another example of using USB which I missed?

thank you all,

[Rob CJ]

Hi Vsurducan,

The datasheet of the 18f14k50 states this:

"For full-speed USB operation, a 48 MHz clock is required for the USB Module. To generate the 48 MHz clock, only two oscillator modes are allowed:

-) EC High-Power mode

-) HS Mode"

I have seen a sample file that runs at 48 MHz but uses the internal oscillator, see 18f67j50_usb_serial.jal.

I am not sure if this answers your question.

Kind regards,

Rob

---

Van: jal...@googlegroups.com <jal...@googlegroups.com> namens vsurducan <vsur...@gmail.com>
Verzonden: donderdag 18 februari 2021 15:09
Aan: jal...@googlegroups.com <jal...@googlegroups.com>
Onderwerp: [jallib] USB issue

 

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[vsurducan]

Thx Rob. You point out the problem well. I'm testing with PIC18F25k50.

With 16MHz HS and 3x PLL the USB communication works ok.

However with 16MHz INTOSC and PLL, I continuously get the same error "USB device has a malfunction..." WIN does not read the USB descriptor, perhaps because of wrong or unstable frequency on the USB module.

On the other hand, PIC18F25K50 USB oscillator description is quite weird:

For low speed, USB module must have a 6MHz clock by setting the LS48MHz bit (table 3.6 page 47 DS30000684B datasheet). This is crystal clear.

For high speed, USB module must have 48MHz, but no description of how to do that is given (table 3.7, the same page).

 Fig.1 at page 29 shows the clock structure for USB. What has to be set to have a 48MHz USB clock?

I will dig more...

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[Oliver Seitz]

Hi!

Allowable clock tolerance for full speed USB is +/- 0.25%. Without the Active Clock Tuning (ACT) Module, the internal oscillator doesn't meet that accuracy. Did you activate that modue?

Greets,
Kiste




Am Freitag, 19. Februar 2021, 07:45:43 MEZ hat vsurducan <vsur...@gmail.com> Folgendes geschrieben:

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[vsurducan]

Hi Oliver,

yes the ACT seems to be activated, but I'm not sure it is properly set.

ACTCON = 0b1001_1000  (90h)                     -- ACT module enabled, INTOSC locked at 0.02% on USB host clock, updates to OSCTUNE

I saw also other weird issues:

-on full speed USB (FSEN = 1, UPUEN=1 ) the pull-up should be set on +D,

-on low speed USB pull-up (FSEN = 0, UPUEN = 1) the pull-up should be on -D, however only pull-up on +D can be observed by measurement.

thx,

Vasile

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[vsurducan]

This issue is not documented on Microchip. There is only one document TB3193 discussing active clock tuning for PIC16LF191XX with the 32KHz secondary oscillator. Below is the config I've tried, it does not work, the ACT is not locking.  I can't understand how the reference clock required for active clock tuning is derived from the USB host as long communication does not work through the USB transceiver without clock.  However some guy reported that ACT feature works with PIC18F25K50: https://www.microchip.com/forums/m847890.aspx.  The smartest gives up....

include 18f25k50                                  -- target PICmicro
pragma target clock 48_000_000            -- oscillator frequency
pragma target PLLSEL        PLL3X         -- PLL multiplier
pragma target PLLEN         ENABLED      -- PLL select
pragma target CPUDIV        P1               -- no divide
pragma target LS48MHz       P8              -- USB 48MHz/8 = 6MHz
pragma target OSC      INTOSC_NOCLKOUT  -- internal OSC
pragma target PCLKEN        ENABLED      -- Primary Oscillator
pragma target FCMEN         DISABLED     -- Fail-Safe Clock Monitor
pragma target IESO          DISABLED     -- Oscillator Switchover mode
pragma target PWRTE         ENABLED      -- power up timer
pragma target BROWNOUT      DISABLED     -- no brownout detection
pragma target LPBOR         DISABLED     -- Low-Power Brown-out Reset
pragma target WDT           CONTROL      -- watchdog software controlled
pragma target PBADEN        DIGITAL      -- digital input port<0..4>
pragma target MCLR          EXTERNAL     -- master reset on MCLR
 pragma target STVR          DISABLED     -- reset on stack over/under flow
 pragma target LVP           DISABLED     -- low-voltage programming
 pragma target ICPRT         DISABLED     -- In-Circuit Debug/Programming Port
 pragma target XINST         DISABLED     -- Extended Instruction Set
 pragma target DEBUG         DISABLED     -- Background Debugger

 WDTCON_SWDTEN = OFF                     -- disable watchdog

 include delay

 include print

OSCCON_IRCF = 0b111                 -- select INTOSC 16MHz
OSCCON_SCS = 0b00                   -- select primary clock defined by CONFIG1H FOSC3:0

ACTCON_ACTEN = 0                     -- ACT module disabled
ACTCON_ACTUD = 0                     -- enable OSCTUNE update
ACTCON_ACTSRC = 1                    -- set HFINTOSC to match with the USB host clock ??
ACTCON_ACTEN = 1                     -- ACT module enabled

UCFG_FSEN = 1                       -- USB full speed mode
UCFG_UPUEN = 1                      -- pull_up enabled
UCFG_UTRDIS = 0                     -- USB transciever enabled
delay_1mS ( 2 )
UCON_USBEN = 1                      -- USB enabled, this bit cannot be enabled without apropiate clock source!

alias  led_lock       is pin_A0      -- alias for pin with LED ACTlock
pin_A0_direction = OUTPUT

alias  led_range       is pin_A1     -- alias for pin with LED OSCTUNE out of range
pin_A1_direction = OUTPUT

alias  led       is pin_A2           -- alias for pin with LED blink
pin_A2_direction = OUTPUT

 for 100 loop
  if ACTCON_ACTLOCK == 0 then
     led_lock = OFF   ; not locked
     delay_1mS ( 1 )
  elsif ACTCON_ACTLOCK == 1 then
     led_lock = ON  ;16MHz ACT locked
  end if
 end loop
 
 if ACTCON_ACTORS == 1 then     ; out of OSCAL range
    led_range = on
 elsif ACTCON_ACTORS == 0 then  ; in the OSCAL range
    led_range = off
 end if

enable_digital_io()                 -- make all pins digital I/O
INTCON_GIE = false
const  byte str_welcome[] = "USB Serial HFINTOSC Demo app\n"

include usb_serial
usb_serial_init()

var bit has_shown_welcome_msg = true
var byte ch = "A"

forever loop
  if ( usb_cdc_line_status() !=  0x00 )  then
        if !has_shown_welcome_msg then
          has_shown_welcome_msg = true
          print_string( usb_serial_data, str_welcome )
         end if
else
          has_shown_welcome_msg = false
end if
        usb_serial_flush()
        usb_serial_data = ch
;        _usec_delay(100_000)
       
   led = ON
   _usec_delay(100_000)
   led = OFF
   _usec_delay(400_000)
end loop