Posted on October 05, 2014 at 11:15@Clive - Well, it took me a little while for what you wrote to click. Yes I now understand and so far all testing is working.
// *******************************************************************
168000000 / 840 = 200000
200000 = 20 * 10000
this.Period = (10000 - 1);
this.Prescalar = (20 - 1);
this.Duration = (10000 / 2);
Output Frequency: 840Hz
// *******************************************************************
168000000 / 160 = 1050000
1050000 = 105 * 10000
this.Period = (10000 - 1);
this.Prescalar = (105 - 1);
this.Duration = (10000 / 2);
Output Frequency: 160Hz
// *******************************************************************
168000000 / 23456 = 7162.3465211459754433833560709413
7162.3465211459754433833560709413 = 2 * 3581
this.Period = (3581- 1);
this.Prescalar = (2 - 1);
this.Duration = (3581/ 2);
Output Frequency: 23.46KHz
// *******************************************************************
So, simple you were right, my in-experience did over look this Clock issue by the looks of it. Some confusion entered the picture: 168000000 / 2 = 84000000 - I real all over the web that APB2 was 84000000 and it is but the calculation you gave is not for the divider product, its for the Clock for APB2. 84000000 is only CK_CNT, not the APB2 Bus Speed: clock frequency = 168000000.
Factoring:
I have written, with some help of quite a few of the good folk's @Stack Exchange, a small application that may help others:
C# Console App:
static void Main(string[] args)
{
double a;
UInt32 Clk = 168000000;
Console.WriteLine(''Please enter Frequency: '');
a = uint.Parse(Console.ReadLine());
// See: P.151 of the STM32F4xx RM0090 User Manual...
// Several prescalers are used to configure the AHB frequency, the high-speed APB (APB2)
// and the low-speed APB (APB1) domains. The maximum frequency of the AHB domain is
// 180 MHz. The maximum allowed frequency of the high-speed APB2 domain is 90 MHz. The
// maximum allowed frequency of the low-speed APB1 domain is 45 MHz
Console.WriteLine(''APB1 Low speed Advanced Peripheral Bus'');
Console.WriteLine(''APB2 High speed Advanced Peripheral Bus'');
uint PxQ = (Clk / Convert.ToUInt32(a));
List<uint> list = Factor(PxQ);
for (int i = 0; i < (list.Count); i++)
{
if (list[i] >= 65535)
{
Console.WriteLine(''Factor is too large: {0}'', list[i]);
}
else
{
if (0 != (i % 2))
{
Console.WriteLine(''Freq {0} = ({1} (Clk) / {2} = Factored Numbers: (P = {3} * Q = {4}))'', a, Clk, PxQ, list[i - 1], list[i]);
}
}
}
Console.ReadLine();
}
/// <summary>
/// Thanks to those involved in getting this excellent Function together!!!
/// See:
http://stackoverflow.com/questions/239865/best-way-to-find-all-factors-of-a-given-number-in-c-sharp
/// This Function has been slightly modified by myself to suit the purposes of this application.
/// </summary>
/// <param name=''number''>Number to get the Factored Numbers for. E.G: (3 * 2) = 6. 6 Being the Number.</param>
/// <returns>List<uint></returns>
public static List<uint> Factor(uint number)
{
List<uint> factors = new List<uint>();
// Round down the Number to check...
uint max = (uint)Math.Sqrt(number);
for (uint factor = 1; factor <= max; ++factor)
{
// Test from 1 to the square root, or the int below it, inclusive...
if (number % factor == 0)
{
factors.Add(factor);
if (factor != number / factor)
{
// Don't add the square root twice! Thanks Jon
factors.Add(number / factor);
}
}
}
return factors;
} Thank You Clive for your help - ST Should put you on staff!!!
All the Best
Chris
