STuW81300 low power

[ngodoanvan]

Hi,
I config STuW81300 with this parameters:

STUW81300_WriteData (ST9_REG, 0x48000000);
STUW81300_WriteData (ST0_REG, 0x02600040);   // N = 64
STUW81300_WriteData (ST8_REG, 0x40080003);
STUW81300_WriteData (ST7_REG, 0x38102004);
STUW81300_WriteData (ST6_REG, 0x30001000);
STUW81300_WriteData (ST5_REG, 0x28000000);
STUW81300_WriteData (ST4_REG, 0x20039315);
STUW81300_WriteData (ST3_REG, 0x1C008002);
STUW81300_WriteData (ST2_REG, 0x14000001);
STUW81300_WriteData (ST1_REG, 0x0D400000);
STUW81300_WriteData (ST0_REG, 0x02600040);

and Read register:

00> Product codes STUW81300T and STUW81300TR
00> ST9 Register: 0x0
00> ST8 Register: 0x80003
00> ST7 Register: 0x102004
00> ST6 Register: 0x1000
00> ST5 Register: 0x0
00> ST4 Register: 0x39315
00> ST3 Register: 0x4008002
00> ST2 Register: 0x4000001
00> ST1 Register: 0x5400000
00> ST0 Register: 0x7E00040
00> ST10 Register: 0x3E0D0

The signal I measured is lower than −20 dBm. This is a screenshot from the spectrum analyzer

please support me fix this problem.
Thank you very much

[Peter BENSCH]

If your question is still relevant despite the age:

There are indications that the STuW81300 is not actually configured as intended, which can explain an output level below −20dBm.

The upper bits are clearly not what you wrote. Examples:

• ST3: written 0x1C008002, read 0x04008002
• ST2: written 0x14000001, read 0x04000001
• ST1: written 0x0D400000, read 0x05400000
• ST0: written 0x02600040, read 0x07E00040

This strongly suggests:

• the SPI frame (bit count, bit order, or timing of LE vs SCK) is not exactly as per datasheet, or
• the address / CO bit is shifted.

If the registers in the chip do not contain what you think, you can easily end up with:

• RF outputs powered down,
• wrong PLL/divider configuration,
• or partially powered-down blocks.

I'd recommend to:

1. Fix SPI first
   • Confirm 32‑bit frames, correct CO & address bits.
   • Write a simple pattern, read back, confirm exact match.
     
     
2. Use the datasheet example configuration
   • Program ST9, ST0, ST8…ST1, ST0 exactly as in section 7.18 of the data sheet
   • Read back ST0…ST8 and verify exact matching values (no bit shifts)
     
     
3. Check lock and LDO status (ST10, LOCK_DET = 1, REG_*_*)
4. Check PD pins and RF enable (PDRF1, PDRF2)
5. Verify RF measurement (RFx_OUTP with proper termination at the unused differential pin, take cable losses into account)

Regards
/Peter

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