Endpoint

Work associated with C# on STM32MP boards

This repository explores the use of C# to manipulate peripheral registers on GHI's Endpoint 'Domino' board. The approach used is to encapsulate registers with a struct and refer to that using the C# ref feature. Each register is represented by a contained struct that contains a single field and a peripheral class contains a member for each distinct register. The register structs are defined within a partial struct for the peripheral and the peripheral class has an auto generated part.

The auto generated part defines a property for each register sub field making the abstraction very close to the technical documentation for the registers. The auto generated struct is created from a textual defintion of the register and its sub fields, here's an example used to create the TimerGeneral partial class file (in the 'Generated' sub folder):

cr1(0x00):     cen(0,1)bool; udis(1,1)bool; urs(2,1)bool; opm(3,1)bool; dir(4,1)bool; cms(6,2)CenterMode; arpe(7,1)bool; ckd(9,2)uint; uifremap(11,1)bool;
cr2(0x4):      ccds(3,1)bool; mms(6,3)MasterMode; ti1s(7,1)bool;
sr(0x10):      uif(0,1)bool; cc1if(1,1)bool; cc2if(2,1)bool; cc3if(3,1)bool; cc4if(4,1)bool; tif(6,1)bool; cc1of(9,1)bool; cc2of(10,1)bool; cc3of(11,1)bool; cc4of(12,1)bool;
ccmr1(0x18):   cc1s(1,2)CC1SMode; oc1fe(2,1)bool; oc1pe(3,1)bool; oc1m(16,1, 6,3)OCMode; oc1ce(7,1)bool; cc2s(9,2)CC2SMode; oc2fe(10,1)bool; oc2pe(11,1)bool; oc2m(24,1,14,3)OCMode; oc2ce(15,1)bool;
cnt_nre(0x24): this(32,1)bool;
cnt_rem(0x24): this(31,1)bool; uifcpy(31,1)bool;
arr(0x2C):     this(31,1)bool;
psc(0x28):     value(15,16)uint;
ccer(0x20):    cc1e(0,1)bool; cc1p(1,1)bool; cc1np(3,1)bool; cc2e(4,1)bool; cc2p(5,1)bool; cc2np(7,1)bool; cc3e(8,1)bool; cc3p(9,1)bool; cc3np(11,1)bool; cc4e(12,1)bool; cc4p(13,1)bool; cc4np(15,1) bool;
ccr1(0x34):    ccr(31,32)uint;

This simple grammar (which is a regular expression grammar) can represent any kind of register and makes it very easy to add register definitions without needing to write any of the intricate boolean expressions for AND and OR and so on. The auto generated struct also includes safety checks that prevent calling code from accidentally setting reserved bits and so on.

Each regdef begins with the register name with it's offset from the peripheral base address. There then follow a sequence of field definitions that start with field name, then a start bit position and length (in bits) followed by the typename used to represent values for the field. These tyope names are expected to be user defined enum defintions.

The generator tool converts all register and field names into uppercase, this makes it easy to edit and type these definitions without having to use uppercase in the defintion. The regular expression defintion for the regdef syntax is defined in Constants.cs like this

        // language=regex
        public const string identifier = @"(([a-zA-Z][a-zA-Z\d]*))";
        // language=regex
        public const string hexnumber = @"0x[0-9A-Fa-f]+";
        // language=regex
        public const string s = @"\s*";
        // language=regex
        public const string lpar = @"\(";
        // language=regex
        public const string rpar = @"\)";
        // language=regex
        public const string colon = @":";
        // language=regex
        public const string commalist = @"\d+(\s*,\s*\d+)+";
        // language=regex
        public const string semicolon = @";";
        // language=regex
        public const string dot = @"\.";
        // language=regex
        public const string Syntax = $@"{identifier}{s}{lpar}{s}{hexnumber}{s}{rpar}{s}{colon}{s}({identifier}({dot}{identifier})?{s}{lpar}{s}{commalist}{s}{rpar}{s}{identifier}{s}{semicolon}{s})+";

The generator logic is part of the class library and will in due course, be managed by a Visual Studio based generator.