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feat: add 16-ring bank, sampled XOR, pair capture and frequency counter (FPGA v2)

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randogoth 2026-10-25 12:56:54 +02:00
parent d51a6c0ca8
commit 504b00752a
12 changed files with 654 additions and 347 deletions
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74
arduino/strix_capture/strix_capture.ino
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@ -1,10 +1,12 @@
// STRIX raw capture tool: boots the STRIX FPGA image and serves raw ring-oscillator
// captures over USB serial for jitter characterization (see tools/capture.py).
// STRIX raw capture tool: boots the STRIX FPGA image and gives the host (tools/jitter.py)
// register access and raw captures over USB serial.
//
// Commands (one per line):
// id print the FPGA identification
// cap <source> <decimation> capture a burst and send it as "DATA <n>\n" + n raw bytes
// source: 0 tap A, 1 enhanced A, 2 enhanced B, 3 pair XOR
// Commands (one per line, numbers in decimal):
// id print the FPGA identification
// r <register> read a register, prints its value
// w <register> <value> write a register, prints "OK"
// cap start a capture with the current settings and send it as
// "DATA <n>\n" followed by n raw bytes
#include <SPI.h>
#include <VidorBoot.h>
@ -18,17 +20,14 @@ const SPISettings STRIX_SPI_SETTINGS(8000000, MSBFIRST, SPI_MODE0);
enum : uint8_t {
REG_ID0 = 0x00,
REG_VERSION = 0x04,
REG_SOURCE = 0x08,
REG_DECIM_HIGH = 0x09,
REG_DECIM_LOW = 0x0A,
REG_CONTROL = 0x0B,
REG_STATUS = 0x0C,
REG_DATA = 0x10,
};
const uint8_t READ = 0x80;
const uint8_t CONTROL_START = 0x01;
const uint8_t STATUS_DONE = 0x02;
const uint8_t CONTROL_START_CAPTURE = 0x01;
const uint8_t STATUS_CAPTURE_DONE = 0x02;
const size_t CAPTURE_BYTES = 32768;
const size_t CHUNK_BYTES = 512;
@ -66,15 +65,12 @@ void printId() {
Serial.println(readRegister(REG_VERSION));
}
void capture(uint8_t source, uint16_t decimation) {
writeRegister(REG_SOURCE, source);
writeRegister(REG_DECIM_HIGH, decimation >> 8);
writeRegister(REG_DECIM_LOW, decimation & 0xFF);
writeRegister(REG_CONTROL, CONTROL_START);
void capture() {
writeRegister(REG_CONTROL, CONTROL_START_CAPTURE);
// 262,144 samples at 120 MHz take up to 143 s at the maximum decimation of 65535.
unsigned long start = millis();
while (!(readRegister(REG_STATUS) & STATUS_DONE)) {
// 262,144 samples at 120 MHz take up to 143 s at the maximum decimation of 65535.
while (!(readRegister(REG_STATUS) & STATUS_CAPTURE_DONE)) {
if (millis() - start > 180000) {
Serial.println("ERR timeout");
return;
@ -93,25 +89,35 @@ void capture(uint8_t source, uint16_t decimation) {
}
}
// Parses "<a>" or "<a> <b>" after the command word; returns the number of values found.
int parseArgs(const String &args, long &a, long &b) {
int space = args.indexOf(' ');
if (args.length() == 0) return 0;
a = args.substring(0, space < 0 ? args.length() : space).toInt();
if (space < 0) return 1;
b = args.substring(space + 1).toInt();
return 2;
}
void handleCommand(String line) {
line.trim();
if (line == "id") {
int space = line.indexOf(' ');
String command = space < 0 ? line : line.substring(0, space);
String args = space < 0 ? "" : line.substring(space + 1);
long reg = 0, value = 0;
int count = parseArgs(args, reg, value);
if (command == "id") {
printId();
} else if (line.startsWith("cap ")) {
int space = line.indexOf(' ', 4);
if (space < 0) {
Serial.println("ERR usage: cap <source> <decimation>");
return;
}
long source = line.substring(4, space).toInt();
long decimation = line.substring(space + 1).toInt();
if (source < 0 || source > 3 || decimation < 1 || decimation > 65535) {
Serial.println("ERR source 0-3, decimation 1-65535");
return;
}
capture(source, decimation);
} else if (command == "r" && count == 1 && reg >= 0 && reg < 0x80) {
Serial.println(readRegister(reg));
} else if (command == "w" && count == 2 && reg >= 0 && reg < 0x80 && value >= 0 && value < 256) {
writeRegister(reg, value);
Serial.println("OK");
} else if (command == "cap") {
capture();
} else if (line.length() > 0) {
Serial.println("ERR unknown command");
Serial.println("ERR unknown or malformed command");
}
}
@ -128,7 +134,7 @@ void setup() {
pinMode(STRIX_SS, OUTPUT);
digitalWrite(STRIX_SS, HIGH);
strixSpi.begin();
// SPIClass::begin() applies the pins' default mux; A3-A6 need SERCOM0's alternate mux.
// SPIClassSAMD::begin() applies the pins' default mux; A3-A6 need SERCOM0's alternate mux.
pinPeripheral(A3, PIO_SERCOM_ALT);
pinPeripheral(A4, PIO_SERCOM_ALT);
pinPeripheral(A6, PIO_SERCOM_ALT);