HAL-based Si5351 driver for STM32.
Si5351 is a I2C-programmable 8 kHz - 160 MHz clock generator made by Silicon Labs. It has 3 ports (or more depending on modification) with 50 Ohm output impedance. The signal level can be changed in ~2-11 dBm range and the phase shift between channels is configurable.
Basic interface:
const int32_t correction = 978;
si5351_Init(correction);
// 28 MHz @ ~7 dBm
si5351_SetupCLK0(28000000, SI5351_DRIVE_STRENGTH_4MA);
// 144 MHz @ ~7 dBm
si5351_SetupCLK2(144000000, SI5351_DRIVE_STRENGTH_4MA);
// Enable CLK0 and CLK2
si5351_EnableOutputs((1<<0) | (1<<2));
Advanced interface, setting up regular mode:
const int32_t correction = 978;
si5351_Init(correction);
si5351PLLConfig_t pll_conf;
si5351OutputConfig_t out_conf;
int32_t Fclk = 7000000; // 7 MHz
si5351_Calc(Fclk, &pll_conf, &out_conf);
si5351_SetupPLL(SI5351_PLL_A, &pll_conf);
si5351_SetupOutput(0, SI5351_PLL_A, SI5351_DRIVE_STRENGTH_4MA, &out_conf, 0);
si5351_EnableOutputs(1<<0);
Advanced interface, setting up I/Q-mode:
const int32_t correction = 978;
si5351_Init(correction);
si5351PLLConfig_t pll_conf;
si5351OutputConfig_t out_conf;
int32_t Fclk = 7000000; // 7 MHz
si5351_CalcIQ(Fclk, &pll_conf, &out_conf);
/*
* `phaseOffset` is a 7bit value, calculated from Fpll, Fclk and desired phase shift.
* To get N° phase shift the value should be round( (N/360)*(4*Fpll/Fclk) )
* Two channels should use the same PLL to make it work. There are other restrictions.
* Please see AN619 for more details.
*
* si5351_CalcIQ() chooses PLL and MS parameters so that:
* Fclk in [1.4..100] MHz
* out_conf.div in [9..127]
* out_conf.num = 0
* out_conf.denum = 1
* Fpll = out_conf.div * Fclk.
* This automatically gives 90° phase shift between two channels if you pass
* 0 and out_conf.div as a phaseOffset for these channels.
*/
uint8_t phaseOffset = (uint8_t)out_conf.div;
si5351_SetupOutput(0, SI5351_PLL_A, SI5351_DRIVE_STRENGTH_4MA, &out_conf, 0);
si5351_SetupOutput(2, SI5351_PLL_A, SI5351_DRIVE_STRENGTH_4MA, &out_conf, phaseOffset);
/*
* The order is important! Setup the channels first, then setup the PLL.
* Alternatively you could reset the PLL after setting up PLL and channels.
* However since _SetupPLL() always resets the PLL this would only cause
* sending extra I2C commands.
*/
si5351_SetupPLL(SI5351_PLL_A, &pll_conf);
si5351_EnableOutputs((1<<0) | (1<<2));
More comments are in the code. See also examples/ directory.
This library was forked from ProjectsByJRP/si5351-stm32 which in it's turn is a port of adafruit/Adafruit_Si5351_Library. Both libraries are licensed under BSD.