From e7dedb761eac9626d581081bc82f1d1dc7d48a14 Mon Sep 17 00:00:00 2001
From: Tobias Schneider <schneider@blinkenlichts.net>
Date: Mon, 8 Jun 2015 00:54:56 +0200
Subject: [PATCH] feat(max2871): First mixer_set_frequency implementation

---
 firmware/common/max2871.c | 127 +++-----------------------------------
 1 file changed, 10 insertions(+), 117 deletions(-)

diff --git a/firmware/common/max2871.c b/firmware/common/max2871.c
index cba655c7..e33692f8 100644
--- a/firmware/common/max2871.c
+++ b/firmware/common/max2871.c
@@ -21,122 +21,6 @@ static void max2871_spi_write(uint8_t r, uint32_t v);
 static void max2871_write_registers(void);
 static void delay_ms(int ms);
 
-/*
- * - The input is fixed to 50 MHz
- * f_REF = 50 MHz
- *
- * - The VCO must operate between 3 GHz and 6 GHz
- * f_VCO range: 3 GHz - 6 GHz
- *
- * Phase Detector Clock:
- *      - We configure the phase detector to not change the
- *        input signal
- *      f_PFD = f_REF x [(1 + DBR)/(R x (1 + RDIV2))]
- *      R = 1
- *      DBR = 0
- *      RDIV2 = 0
- *
- *      => f_PFD = 50 MHz
- *
- *
- * f_RFOUT < 3 GHz:
- *  - To go to < 3 GHz, f_VCO has to be divided.
- *  f_RFOUT = f_VCO / DIVA
- *
- *  - We just divide by 2 for now
- *  DIVA = 2
- *  => f_RFOUT = f_VCO / 2
- *  
- *  - Relationship between f_PFD (fixed) and f_VCO (variable)
- *  N + (F/M) = f_VCO/ f_PFD
- *
- *  - Insert relationship between f_RFOUT and f_VCO:
- *  N + (F/M) = (f_RFOUT * 2) / f_PFD
- *  f_RFOUT = (N + F/M) * f_PFD / 2
- *
- *  - Limits for N, M and F from the datasheet:
- *  19 <= N <= 4091
- *  2  <= M <= 4095
- *  F < M
- *
- *  - Plug in constants:
- *  f_RFOUT = (N + F/M) / 2 * 50 MHz
- *
- *  - Given the range of N, we can go to:
- *  f_RFOUT range: 475 MHz - 3 GHz
- *
- *  - N steps in 25 MHz increments:
- *  N = floor(f_RFOUT / 50 MHz * 2)
- *      => N = (f_RFOUT * 2) / 50 MHz (uses integer math)
- *
- *  - Calculate the error:
- *  f_int_ERROR = f_RFOUT - (N * 50 MHz) / 2
- *  f_int_ERROR range: 0 MHz - 24 MHz
- *
- *  - Use the fraction to get to the correct frequency:
- *  (F/M) / 2 * 50 MHz = f_int_ERROR
- *
- *  - Fix M:
- *  M = 25
- * 
- *  - Calculate F:
- *  (F/25) / 2 * 50 MHz = f_int_ERROR
- *  F = f_int_ERROR / 1 MHz
- *
- *  - Calculate the new error:
- *
- *  f_ERROR = f_RFOUT - (N + F/M) / 2 * 50 MHz
- *  f_ERROR range: 0 MHz - 1 MHz
- *
- *
- * f_RFOUT > 3 GHz:
- *  - Do not divide the VCO output
- *  DIVA = 1
- *  => f_RFOUT = f_VCO
- *
- *  - Relationship between f_PFD (fixed) and f_VCO (variable)
- *  N + (F/M) = f_VCO/ f_PFD
- *
- *  - Insert relationship between f_RFOUT and f_VCO:
- *  N + (F/M) = f_RFOUT / f_PFD
- *  f_RFOUT = (N + F/M) * f_PFD
- *
- *  - Limits for N, M and F from the datasheet:
- *  19 <= N <= 4091
- *  2  <= M <= 4095
- *  F < M
- *
- *  - Plug in constants:
- *  f_RFOUT = (N + F/M) * 50 MHz
- *
- *  - Given the range of N and the VCO limits, we can go to:
- *  f_RFOUT range: 3000 MHz - 6000 MHz
- *
- *  - N steps in 50 MHz increments:
- *  N = floor(f_RFOUT / 50 MHz)
- *      => N = f_RFOUT / 50 MHz (uses integer math)
- *
- *  - Calculate the error:
- *  f_int_ERROR = f_RFOUT - N * 50 MHz
- *  f_int_ERROR range: 0 MHz - 49 MHz
- *
- *  - Use the fraction to get to the correct frequency:
- *  (F/M) * 50 MHz = f_int_ERROR
- *
- *  - Fix M:
- *  M = 50
- * 
- *  - Calculate F:
- *  (F/50) * 50 MHz = f_int_ERROR
- *  F = f_int_ERROR / 1 MHz
- *
- *  - Calculate the new error:
- *
- *  f_ERROR = f_RFOUT - (N + F/M) * 50 MHz
- *  f_ERROR range: 0 MHz - 1 MHz
- *
- */
-
 void mixer_setup(void)
 {
 	/* Configure GPIO pins. */
@@ -291,7 +175,16 @@ static void max2871_write_registers(void)
 /* Set frequency (MHz). */
 uint64_t mixer_set_frequency(uint16_t mhz)
 {
-    (void) mhz;
+    int n = mhz;
+    int diva = 0;
+
+    while(n < 3000) {
+        n *= 2;
+        diva += 1;
+    }
+
+    max2871_set_N(n);
+    max2871_set_DIVA(diva);
     return mhz;
 }