NASR-M board bring-up, LMK03328 clock Zephyr OS driver
The LMK03328 clock driver is finally functional. Today, I was happily observing a sine-like signal at 33.33 MHz on the screen of my good old scope. I suppose it’s really a meander. Once I get a faster oscilloscope, I’ll be able to tell with confidence. What disappointed me was the low amplitude. The peak value was around 1.76 - 1.8V despite the 3.3V at the line #3 IO supply. The datasheet of LMK03328 states the following: “The 1.8-V LVCMOS driver supports rail-to-rail output swing only when powered from VDDO = 1.8 V +/- 5% (recommended VDDO for use with LVCMOS output format). VOH level is NOT rail-to-rail for VDDO = 2.5 V or 3.3 V due to the dropout voltage of the output channel’s internal LDO regulator.”
My expectation for peak amplitude was 2V or a little more. Let’s hope it's enough to clock the SOC. The driver for Zephyr OS is in a NASR-M-ZFW source tree. It’s a really simple one. First, it reads the register values described in a DTS, and then transfers them via the I2C. It works for me, and frankly speaking, I don’t want to spend any more time on this. At first, I tried to transfer the entire register config generated by TICS Pro, but that didn’t work. After a few tries, I had to cut out all register definitions that weren't related to the PLL or outputs, and it finally worked as expected.
Here is a DTS example:
lmk03328: lmk03328@54 {
compatible = "ti,lmk03328";
init-priority = <90>;
reg = <0x54>;
/*software-reset;*/ /* clear R12[7] after writing all registers */
status = "okay";
reg-values = <
0x1D01 /* R29 enable AC coupling mode on a primary input*/
0x0232 /* R2 addr=0x02 val=0x32 */
0x0300 /* R3 addr=0x03 val=0x00 */
0x0CDF /* R12 addr=0x0C val=0xDF */
0x0D00 /* R13 addr=0x0D val=0x00 */
0x0E00 /* R14 addr=0x0E val=0x00 */
0x1800 /* R24 addr=0x18 val=0x00 */
0x19F5 /* R25 addr=0x19 val=0xF5 */
0x14FF /* R20 addr=0x14 val=0xFF */
0x15FF /* R21 addr=0x15 val=0xFF */
0x16FF /* R22 addr=0x16 val=0xFF */
0x1702 /* R23 addr=0x17 val=0x02 */
0x1B58 /* R27 addr=0x1B val=0x58 */
0x1C28 /* R28 addr=0x1C val=0x28 */
0x1D03 /* R29 addr=0x1D val=0x03 */
0x1E0C /* R30 addr=0x1E val=0x0C */
0x1F20 /* R31 addr=0x1F val=0x20 */
0x2030 /* R32 addr=0x20 val=0x30 */
0x2127 /* R33 addr=0x21 val=0x27 */
0x2230 /* R34 addr=0x22 val=0x30 */
0x237C /* R35 addr=0x23 val=0x7C */
0x2427 /* R36 addr=0x24 val=0x27 */
0x2510 /* R37 addr=0x25 val=0x10 */
0x262F /* R38 addr=0x26 val=0x2F */
0x2710 /* R39 addr=0x27 val=0x10 */
0x282F /* R40 addr=0x28 val=0x2F */
0x2950 /* R41 addr=0x29 val=0x50 */
0x2A0E /* R42 addr=0x2A val=0x0E */
0x790F /* R121 addr=0x79 val=0x0F */
0x7A0F /* R122 addr=0x7A val=0x0F */
0x7B0F /* R123 addr=0x7B val=0x0F */
0x7C0F /* R124 addr=0x7C val=0x0F */
0x2B50 /* R43 addr=0x2B val=0x50 */
0x2C0E /* R44 addr=0x2C val=0x0E */
0x2D0A /* R45 addr=0x2D val=0x0A */
0x2E00 /* R46 addr=0x2E val=0x00 */
0x2F00 /* R47 addr=0x2F val=0x00 */
0x30FF /* R48 addr=0x30 val=0xFF */
0x3205 /* R50 addr=0x32 val=0x05 */
0x3303 /* R51 addr=0x33 val=0x03 */
0x3400 /* R52 addr=0x34 val=0x00 */
0x3500 /* R53 addr=0x35 val=0x00 */
0x3600 /* R54 addr=0x36 val=0x00 */
0x3700 /* R55 addr=0x37 val=0x00 */
0x380E /* R56 addr=0x38 val=0x0E */
0x3915 /* R57 addr=0x39 val=0x15 */
0x3A00 /* R58 addr=0x3A val=0x00 */
0x3B62 /* R59 addr=0x3B val=0x62 */
0x3C00 /* R60 addr=0x3C val=0x00 */
0x3D00 /* R61 addr=0x3D val=0x00 */
0x8407 /* R132 addr=0x84 val=0x07 */
0x8505 /* R133 addr=0x85 val=0x05 */
0x3E22 /* R62 addr=0x3E val=0x22 */
0x3F00 /* R63 addr=0x3F val=0x00 */
0x4000 /* R64 addr=0x40 val=0x00 */
0x412D /* R65 addr=0x41 val=0x2D */
0x4203 /* R66 addr=0x42 val=0x03 */
0x431A /* R67 addr=0x43 val=0x1A */
0x4403 /* R68 addr=0x44 val=0x03 */
0x457D /* R69 addr=0x45 val=0x7D */
0x4607 /* R70 addr=0x46 val=0x07 */
0x4712 /* R71 addr=0x47 val=0x12 */
0x4818 /* R72 addr=0x48 val=0x18 */
0x4900 /* R73 addr=0x49 val=0x00 */
0x4A5A /* R74 addr=0x4A val=0x5A */
0x4B00 /* R75 addr=0x4B val=0x00 */
0x4C00 /* R76 addr=0x4C val=0x00 */
0x4D00 /* R77 addr=0x4D val=0x00 */
0x5001 /* R80 addr=0x50 val=0x01 */
0x510C /* R81 addr=0x51 val=0x0C */
0x5208 /* R82 addr=0x52 val=0x08 */
0x5301 /* R83 addr=0x53 val=0x01 */
0x5404 /* R84 addr=0x54 val=0x04 */
0x5507 /* R85 addr=0x55 val=0x07 */
0x5600 /* R86 addr=0x56 val=0x00 */
0x5700 /* R87 addr=0x57 val=0x00 */
>;
};
Now that the clock works, I can start soldering the flash storage and supporting circuitry.