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Segmentation fault when trying to read python process memory on Mac OS

I was trying to figure out how the Mach VM Api works as there is almost 0 documentation around it and to do that I was messing around with reading/writing to other processes' memory.
To start I basically created a c program that constantly printed a string and its address. Then I used this program to try modifying the string mid execution and it worked fine:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <libproc.h>
#include <mach/mach.h>
#include <mach/mach_vm.h>
#define EXIT_ON_MACH_ERROR(msg, retval) \
if (kr != KERN_SUCCESS) { mach_error(msg ":" , kr); exit((retval)); }
uint32_t* get_pids(uint16_t* size) {
// Gets all PIDS on the system to locate specific PID later. Probably inefficient
// but I don't care
uint32_t number_of_pids = proc_listpids(1, 0, NULL, 0);
uint32_t* buffer = malloc(sizeof(uint32_t) * number_of_pids);
uint8_t return_code = proc_listpids(1, 0, buffer, sizeof(buffer) * number_of_pids);
uint16_t sum = 0;
for(int i = 0; i < number_of_pids; i++) {
if(buffer[i] != 0) {
sum++;
}
}
uint32_t* final = malloc(sizeof(uint32_t) * sum);
for(int i = 0, t = 0; i < number_of_pids; i++) {
if(buffer[i]) {
final[t++] = buffer[i];
}
}
*size = sum;
return final;
}
int main() {
// Locate correct PID according to process name
uint16_t size;
uint32_t* pids = get_pids(&size);
uint16_t maxpathlength = 1024;
uint16_t path_size = maxpathlength * 4;
char path_buffer[path_size];
uint32_t process_pid = 0;
for(int i = 0; i < size; i++) {
memset(path_buffer, '\0', sizeof(path_buffer));
uint8_t return_code = proc_pidpath(pids[i], path_buffer, path_size);
if(strstr(path_buffer, "Python")) {
printf("%d\n", i);
process_pid = pids[i];
}
//printf("PID: %d, Process: %s\n", pids[i], path_buffer);
}
printf("%d\n", process_pid);
struct proc_taskallinfo pro_info;
uint32_t status = proc_pidinfo(process_pid, PROC_PIDTASKALLINFO, 0, &pro_info, sizeof(pro_info));
printf("Python PID: %d\n", process_pid);
printf("Self PID: %d\n", mach_host_self());
mach_port_t port = 0;
kern_return_t kr = task_for_pid(mach_task_self(), process_pid, &port);
EXIT_ON_MACH_ERROR("task_for_pid", kr);
printf("Port: %d\n\n\n", port);
// STUFF
mach_vm_address_t address = 0x102d4b770;
mach_vm_address_t address_a = 0x102d4b770;
char data[50] = "wow";
vm_offset_t buf;
mach_msg_type_number_t sz;
// MEMORY DEALLOCATION
kern_return_t suc = mach_vm_deallocate(port, (mach_vm_address_t) address, (mach_vm_size_t) 1000);
if (suc!=KERN_SUCCESS)
{
printf("mach_vm_deallocate() failed with message %s!\n", mach_error_string(suc));
}
// MEMORY ALLOCATION
kern_return_t all_suc = mach_vm_allocate(port, (mach_vm_address_t *) &address_a, (vm_size_t) 26, false);
if (all_suc!=KERN_SUCCESS)
{
printf("mach_vm_allocate() failed with message %s!\n", mach_error_string(all_suc));
}
// WRITE TO MEMORY
kern_return_t success = mach_vm_write(port, (vm_address_t) address, (vm_address_t)data, 26);
if (success!=KERN_SUCCESS)
{
printf("mach_vm_write() failed with message %s!\n", mach_error_string(success));
}
// READ FROM MEMORY
kern_return_t read_success = mach_vm_read(port, (vm_address_t) 0x6000018c4030, 26, &buf, &sz);
if (read_success!=KERN_SUCCESS)
{
printf("mach_vm_read() failed with message %s!\n", mach_error_string(read_success));
}
char * newstr = (char *) buf;
printf("%s\n", newstr);
return 0;
}
address and address_a were entered manually after figuring out the variable's address. However, when I tried this with a python process where I again just constantly printed out the string and address, I got the following error message the instant I ran the code above:
zsh: segmentation fault python3 strtest.py
I have no knowledge about CPython, so even after playing around a bit and trying to make it work, nothing happened. How can I make this work even on programs? I know its possible as Bit-Slicer made it work but I wasn't able to found out how.

Trying to program ESP32 with manual switch feedback

i want to make a program where i can manage appliances using MQTT messages as well as i want to take feedback using normal switches, i tried the following code but in that case switch one and relay on is operating as expected but switch2 & switch 3 are getting called in loop and switch 2 is automatically getting converted from 0 to 1 and hence if condition is getting verified and its getting in loop, please help
#include <WiFi.h>
#include <PubSubClient.h>
#include "ArduinoJson.h"
#define relayOne 15
#define switchOne 32
#define relayTwo 2
#define switchTwo 35
#define relayThree 4
#define switchThree 34
#define relayFour 22
#define switchFour 39
const char* ssid = "*******";//replace this with your wifi access point
const char * password = ""*******";//"; //replace with your wifi password
const char * host = "*.*.*.*"; //IP address of machine on which broker is installed
const int port = 1883;
const char * mqttUser = "user";
const char * mqttPassword = "user";
WiFiClient espClient;
PubSubClient client(espClient);
StaticJsonBuffer < 55 > jsonBuffer;
void callback(char * topic, byte * payload, unsigned int length) {
Serial.print("Message received in topic: ");
Serial.print(topic);
Serial.print(" length is:");
Serial.println(length);
Serial.print("Data Received From Broker:");
String messageTemp;
for (int i = 0; i < length; i++) {
messageTemp += (char) payload[i];
}
//Serial.println(messageTemp);
const size_t capacity = JSON_OBJECT_SIZE(2) + 20;
DynamicJsonBuffer jsonBuffer(capacity);
//const char* json = "{\"pin\":14,\"value\":1}";
const char * json = messageTemp.c_str();
JsonObject & root = jsonBuffer.parseObject(json);
int pin = root["pin"];
int value = root["value"];
Serial.println(pin);
Serial.println(value);
digitalWrite(pin, value);
}
void setup() {
Serial.begin(115200);
pinMode(relayOne, OUTPUT);
pinMode(switchOne, INPUT_PULLUP);
pinMode(relayTwo, OUTPUT);
pinMode(switchTwo, INPUT_PULLUP);
pinMode(relayThree, OUTPUT);
pinMode(switchThree, INPUT_PULLUP);
pinMode(relayFour, OUTPUT);
pinMode(switchFour, INPUT_PULLUP);
WiFi.begin(ssid, password);
Serial.println("Connecting to WiFi..");
while (WiFi.status() != WL_CONNECTED) {
delay(100);
yield();
}
Serial.println("Connected to the WiFi network");
client.setServer(host, port);
client.setCallback(callback);
while (!client.connected()) {
Serial.println("Connecting to MQTT...");
if (client.connect("ESP8266Client", mqttUser, mqttPassword)) {
Serial.println("connected to MQTT broker");
} else {
Serial.print("failed with state ");
Serial.print(client.state());
delay(500);
}
}
Serial.println("ESP32 AS SUBSCRIBER");
client.subscribe("IOT"); //topic name="Sub"
}
void MQTTPOST(int pin, int value)
{
Serial.println("in mqttpost");
//payload formation begins here
String payload ="{";
payload +="\"Pin\":"; payload +=pin; payload +=",";
payload +="\"Value\":"; payload +=value;
payload +="}";
char attributes[1000];
payload.toCharArray( attributes, 1000 );
client.publish("IOT1", attributes); //topic="Pub" MQTT data post command.
Serial.println( attributes );
Serial.println("");
}
int switchOneValue = 0;
int switchTwoValue = 0;
int switchThreeValue = 0;
int switchFourValue = 0;
void loop() {
client.loop();
int valueSwitchOne = digitalRead(switchOne);
Serial.println(valueSwitchOne);
Serial.println(switchOneValue);
if(valueSwitchOne == 0 && switchOneValue == 0){
digitalWrite(relayOne, 1);
switchOneValue = 1;
MQTTPOST(relayOne, 1);
Serial.println("on");
delay(200);
}else if(valueSwitchOne == 1 && switchOneValue == 1) {
digitalWrite(relayOne, 0);
switchOneValue = 0;
MQTTPOST(relayOne, 0);
Serial.println("off");
delay(200);
}
int valueSwitchTwo = digitalRead(switchTwo);
Serial.println(valueSwitchTwo);
Serial.println(switchTwoValue);
delay(1000);
if(valueSwitchTwo == 0 && switchTwoValue == 0){
digitalWrite(relayTwo, 1);
switchTwoValue = 1;
MQTTPOST(relayTwo, 1);
Serial.println("on2");
delay(200);
}else if(valueSwitchTwo == 1 && switchTwoValue == 1) {
digitalWrite(relayTwo, 0);
switchTwoValue = 0;
MQTTPOST(relayTwo, 0);
Serial.println("off2");
delay(200);
}
int valueSwitchThree = digitalRead(switchThree);
if(valueSwitchThree == 0 && switchThreeValue == 0){
digitalWrite(relayThree, 1);
switchThreeValue = 1;
MQTTPOST(relayThree, 1);
Serial.println("on");
delay(200);
}else if(valueSwitchThree == 1 && switchThreeValue == 1) {
digitalWrite(relayThree, 0);
switchThreeValue = 0;
MQTTPOST(relayThree, 0);
Serial.println("off");
delay(200);
}
}

here is a quote from documentation on esp32:
Appendix A – ESP32 Pin Lists
A.1. Notes on ESP32 Pin Lists
Table 24: Notes on ESP32 Pin Lists
GPIO pins 34-39 are input-only. These pins do NOT feature an output
driver or internal pull-up/pull-down circuitry.
digitalRead() can return arbitrary value for those pins because there are no built-in pull-up resistors there - they are effectively dangling in the air.
It means that following code CAN NOT WORK without external pull-up resistors:
#define switchTwo 35
#define switchThree 34
#define switchFour 39
pinMode(switchTwo, INPUT_PULLUP); // THIS DOES NOT WORK for GPIOs: 34-39!!!
pinMode(switchThree, INPUT_PULLUP); // THIS DOES NOT WORK for GPIOs: 34-39 !!!
pinMode(switchFour, INPUT_PULLUP); // THIS DOES NOT WORK for GPIOs: 34-39 !!!
// unpredictable values are here when button is not pressed
int valueSwitchTwo = digitalRead(35);
int valueSwitchThree = digitalRead(34);
Solution:
either use different pins for the switches
or add real hardware resistors into your schematics

Python ctypes cannot get long string value returned from .so file

I am learning C and trying to import a .so into my python file for higher performance by using a python package ctypes. So everything going well until I had a hard time when trying to get a string returned from .so file.
C code:
char *convert_to_16(char *characters, int n){
char sub_buffer[3];
char code[3];
char *buffer = (char*)malloc(sizeof(characters) * 2);
for(int i=0; i < n; i++){
strncpy(code, characters+i, 1);
sprintf(sub_buffer, "%x", *code);
strncat(buffer, sub_buffer, 2);
}
return buffer;
}
// main() only for test
int main(){
char param[] = "ABCDEFGHTUIKLL";
printf("%s\n", param);
int length = strlen(param);
printf("%s\n", convert_to_16(param, length));
}
It runs well with output:
41424344454647485455494b4c4c
Python code :
c_convert_to_16 = ctypes.CDLL('./convert_to_16.so').convert_to_16
c_convert_to_16.restype = ctypes.c_char_p
a_string = "ABCDEFGHTUIKLL"
new_16base_string = c_convert_to_16(a_string, len(a_string))
print new_16base_string
It runs but only returns two characters:
41
I read the official doc and set restype as ctypes.c_char_p, and try to set it to other values. But it seems it's the only option, just oddly only two characters were returned.
Is it the problem of my ctypes configuration or my C wasn't written correctly?
Many thanks.

I don't know much about ctypes in python but you should create your string like that c_char_p("ABCDEFGHTUIKLL").
And maybe tell what argument take your function c_convert_to_16.argtypes = [c_char_p, c_size_t]
This will fix your undefined behavior in C:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char *convert_to_16(char const *array, size_t const len);
char *convert_to_16(char const *array, size_t const len) {
size_t const len_buffer = len * 2 + 1;
char *buffer = malloc(len_buffer);
if (buffer == NULL) {
return NULL;
}
size_t used = 0;
for (size_t i = 0; i < len; i++) {
if (len_buffer < used || len_buffer - used < 3) {
free(buffer);
return NULL;
}
int ret = snprintf(buffer + used, 3, "%.2x", (unsigned char)array[i]);
if (ret != 2) {
free(buffer);
return NULL;
}
used += 2;
}
return buffer;
}
int main(void) {
char const param[] = "ABCDEFGHTUIKLL";
printf("%s\n", param);
char *ret = convert_to_16(param, sizeof param - 1);
if (ret != NULL) {
printf("%s\n", ret);
}
free(ret);
}

Python ctypes : OSError undefined symbol when loading library

In Ubuntu 14.04, I wrote a C file called hash.c:
/* hash.c: hash table with linear probing */
typedef struct {
void *key;
void *value;
} ht_entry;
typedef struct {
ht_entry *table;
int len;
int num_entries;
int (*hash_fn)(void *key);
int (*key_cmp)(void *k1, void *k2);
} hashtable;
and compiled it with
gcc -shared hash.c -o test.so -fPIC
Afterwards, I tried to load test.so in a Python script (for testing), but I got the following error: "OSError: .../test.so: undefined symbol: hash_fn"
hash_fn is a function pointer in the hashtable struct. It is referenced a number of times by functions later in the file.
I do not understand why this error is happening. I have Googled but all other cases either concern C++ or includes. In my case I just have 1 C file that includes only stdio and stdlib.
here is the FULL code.
When I comment out all but hash_create and print_info, it loads succesfully. When I uncomment find(), it the error happens.
(print_info is just for testing that ctypes works)
/* hash.c: hash table with linear probing */
#include <stdio.h>
#include <stdlib.h>
typedef struct {
void *key;
void *value;
} ht_entry;
typedef struct {
ht_entry *table;
int len;
int num_entries;
int (*hash_fn)(void *key);
int (*key_cmp)(void *k1, void *k2);
} hashtable;
static void close_gap(hashtable *ht, int i);
static int find(hashtable *ht, void *key);
hashtable* hash_create(int len, int (*hash_fn)(void*), int (*key_cmp)(void*, void*))
{
hashtable* ht = (hashtable*) malloc(sizeof(hashtable));
ht->len = len;
ht->table = calloc(len, sizeof(ht_entry));
ht->hash_fn = hash_fn;
ht->key_cmp = key_cmp;
ht->table[0].key = 2;
ht->table[0].value = 3;
return ht;
}
void print_info(hashtable *ht)
{
printf("%d, %d, %d\n", ht->len, ht->table[0].key, ht->table[0].value);
}
void* hash_retrieve(hashtable* ht, void *key)
{
int i = find(ht, key);
if(i < 0) {
return NULL;
}
return ht->table[i].value;
}
void hash_insert(hashtable* ht, void *key, void *value)
{
if(ht->num_entries == ht->len) {
return;
}
int i = hash_fn(key) % ht->len;
while(ht->table[i].key != NULL) {
i = (i + i) % ht->len;
}
ht->table[i].key = key;
ht->table[i].value = value;
}
void hash_remove(hashtable *ht, void *key)
{
int i = find(ht, key);
if(i < 0) {
return;
}
ht->table[i].key = 0;
ht->table[i].value = 0;
close_gap(ht, i);
}
static int find(hashtable *ht, void *key)
{
int i = hash_fn(key) % ht->len;
int num_checked = 0;
while(ht->table[i].key && num_checked != ht->len) {
if(!ht->key_cmp(ht->table[i].key, key)) {
return i;
}
num_checked++;
i = (i + i) % ht->len;
}
return -1;
}
static void close_gap(hashtable *ht, int i)
{
int j = (i + 1) % ht->len;
while(ht->table[j].key) {
int loc = ht->hash_fn(ht->table[j].key);
if((j > i && (loc <= i || loc > j)) || (j < i && (loc <= i && loc > j))) {
ht->table[i] = ht->table[j];
ht->table[j].key = 0;
ht->table[j].value = 0;
close_gap(ht, j);
return;
}
}
}

When I use your compilation line I get five warnings. There are several problems here. First you are trying to assign an int to void * in several places. That raises a warning, and it would crash at runtime because you are passing 2 and 3 as addresses.
Second, you are calling hash_fn in a couple of places instead of ht->hash_fn. That causes the linker error, but you should consider my other changes, otherwise it will crash at runtime with a SIGSEGV:
/* hash.c: hash table with linear probing */
#include <stdio.h>
#include <stdlib.h>
typedef struct {
void *key;
void *value;
} ht_entry;
typedef struct {
ht_entry *table;
int len;
int num_entries;
int (*hash_fn)(void *key);
int (*key_cmp)(void *k1, void *k2);
} hashtable;
static void close_gap(hashtable *ht, int i);
static int find(hashtable *ht, void *key);
hashtable* hash_create(int len, int (*hash_fn)(void*), int (*key_cmp)(void*, void*))
{
hashtable* ht = (hashtable*) malloc(sizeof(hashtable));
ht->len = len;
ht->table = calloc(len, sizeof(ht_entry));
ht->hash_fn = hash_fn;
ht->key_cmp = key_cmp;
// <<< Code changed here
/*
ht->table[0].key = 2;
ht->table[0].value = 3;
*/
{
int *p = malloc(sizeof(int));
*p = 2;
ht->table[0].key = p;
p = malloc(sizeof(int));
*p = 3;
ht->table[0].value = p;
}
// end of code change
return ht;
}
void print_info(hashtable *ht)
{
// <<<< Code changed
printf("%d, %d, %d\n", ht->len,
*(int *)ht->table[0].key, *(int *)ht->table[0].value);
}
void* hash_retrieve(hashtable* ht, void *key)
{
int i = find(ht, key);
if(i < 0) {
return NULL;
}
return ht->table[i].value;
}
void hash_insert(hashtable* ht, void *key, void *value)
{
if(ht->num_entries == ht->len) {
return;
}
// <<< Code changed
int i = ht->hash_fn(key) % ht->len;
while(ht->table[i].key != NULL) {
i = (i + i) % ht->len;
}
ht->table[i].key = key;
ht->table[i].value = value;
}
void hash_remove(hashtable *ht, void *key)
{
int i = find(ht, key);
if(i < 0) {
return;
ht->table[i].key = 0;
ht->table[i].value = 0;
close_gap(ht, i);
}
static int find(hashtable *ht, void *key)
{
// <<< Code changed
int i = ht->hash_fn(key) % ht->len;
int num_checked = 0;
while(ht->table[i].key && num_checked != ht->len) {
if(!ht->key_cmp(ht->table[i].key, key)) {
return i;
}
num_checked++;
i = (i + i) % ht->len;
}
return -1;
}
static void close_gap(hashtable *ht, int i)
{
int j = (i + 1) % ht->len;
while(ht->table[j].key) {
int loc = ht->hash_fn(ht->table[j].key);
if((j > i && (loc <= i || loc > j)) || (j < i && (loc <= i && loc > j))) {
ht->table[i] = ht->table[j];
ht->table[j].key = 0;
ht->table[j].value = 0;
close_gap(ht, j);
return;
}
}
}
I only coded around the errors and warnings, I did not check the logic. You will see that I have used malloc to allocate memory for key and value. Obviously you will need memory management on these two (i.e. free()).

Rate-limiting in python/arduino client/server communication

I'm trying to make a python client communicate with an arduino server. The python client asks the server to take a measurement from the sonar, and then server just sends a confirmation message and then takes the message.
The client:
client.py
import socket
import time
while True:
try:
client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client_socket.connect(("192.168.0.250", 10220))
data = "GET\nSONAR\n\n"
print 'send to server: ' + data
client_socket.send(data)
receive = client_socket.recv(2048)
print receive
client_socket.close()
time.sleep(0.1)
except Exception as msg:
print msg
and the server:
server.ino
#include <avr/wdt.h>
#include <SPI.h>
#include <Ethernet.h>
#include <SoftwareSerial.h>
//localClient parameters, for sending data to the server.
byte mac[] = {0x90, 0xA2, 0xDA, 0x0F, 0x03, 0x58};
byte ip[] = {192,168,0,250};
byte server[] = {192, 168, 0, 100};
int serverPort = 8220;
//Server parameters, for acting like a server.
int pollPort = serverPort + 2000;
EthernetServer pollServer = EthernetServer(pollPort);
//char inString[32]; // string for incoming serial data
//sonar stuff
String content_string;
int NUM_SONARS = 1;
int sonarPin[] = {2, 3, 4, 5};
int triggerPin = 6;
int sonarThreshold = 12.0;
int sonarState[] = {0, 0, 0, 0};
long pulse;
int numPulses = 3;
int pulseArray[] = {0,0,0,0,0};
int filteredMode = 0;
float time;
void setup() {
Serial.begin(9600);
Ethernet.begin(mac, ip);
wdt_enable(WDTO_8S);
pollServer.begin();
for(int i = 0; i < NUM_SONARS; i++) {
pinMode(sonarPin[i], INPUT);
}
pinMode(triggerPin, OUTPUT);
digitalWrite(triggerPin, LOW);
time = 0;
}
void loop() {
wdt_reset();
time = millis();
EthernetClient pollClient = pollServer.available();
if (pollClient) {
boolean currentLineIsBlank = true;
String receivingString = "";
while (pollClient.connected()) {
//while the socket is open
if(pollClient.available()) {
//and there is something to read on the port, then read the available characters
char c = pollClient.read();
receivingString += c;
if (c == '\n' && currentLineIsBlank) {
Serial.print("String received -- ");
Serial.print(receivingString);
Serial.print("at ");
Serial.println(time);
pollClient.println("Received message.");
break;
}
if (c == '\n') {
// you're starting a new line
currentLineIsBlank = true;
}
else if (c != '\r') {
// you've gotten a character on the current line
currentLineIsBlank = false;
}
}
}
// give the web browser time to receive the data
delay(1);
// parse the incoming data
String command = split(receivingString,'\n',0);
String payload = split(receivingString,'\n',1);
String key = split(payload,'=',0);
String value = split(payload,'=',1);
//PARSE THE KEY AND VALUE NOW
if(command == "GET") {
//if I received a GET command, send a response to the client.
if(key == "SONAR") {
pingSonars();
}
}
}
String split(String data, char delimiter, int index) {
int found = 0;
int strIndex[] = {0, -1};
int maxIndex = data.length()-1;
for(int i=0; i<=maxIndex && found<=index; i++){
if(data.charAt(i)==delimiter || i==maxIndex){
found++;
strIndex[0] = strIndex[1]+1;
strIndex[1] = (i == maxIndex) ? i+1 : i;
}
}
return found>index ? data.substring(strIndex[0], strIndex[1]) : "";
}
void isort(int *a, int n) {
for (int i = 1; i < n; ++i) {
int j = a[i];
int k;
for (k = i - 1; (k >= 0) && (j < a[k]); k--) {
a[k + 1] = a[k];
}
a[k + 1] = j;
}
}
int mode(int *x,int n){
int i = 0;
int count = 0;
int maxCount = 0;
int mode = 0;
int bimodal;
int prevCount = 0;
while(i<(n-1)){
prevCount=count;
count=0;
while(x[i]==x[i+1]){
count++;
i++;
}
if(count>prevCount&count>maxCount){
mode=x[i];
maxCount=count;
bimodal=0;
}
if(count==0){
i++;
}
if(count==maxCount){//If the dataset has 2 or more modes.
bimodal=1;
}
if(mode==0||bimodal==1){//Return the median if there is no mode.
mode=x[(n/2)];
}
return mode;
}
}
void printArray(int *a, int n) {
for (int i = 0; i < n; i++)
{
Serial.print(a[i], DEC);
Serial.print(' ');
}
Serial.println();
}
void pingSonars() {
digitalWrite(6, HIGH);
for(int i = 0; i < NUM_SONARS; i++) {
for(int j = 0; j < numPulses; j++) {
pulse = pulseIn(sonarPin[i], HIGH);
pulseArray[j] = pulse/147; //convert to inches -- 147 uS per inches
delay(5);
}
isort(pulseArray, numPulses);
filteredMode = mode(pulseArray,numPulses);
//printArray(pulseArray,numPulses);
Serial.print("Filtered distance for Sonar ");
Serial.print(i);
Serial.print(": ");
Serial.println(filteredMode);
if((filteredMode < sonarThreshold) && !sonarState[i]) {
//if we are closer than the threshold and previously were not, this is a rising edge:
Serial.print("Sonar ");
Serial.print(i);
Serial.println(" triggered!");
sonarState[i] = 1;
}
else if (filteredMode > sonarThreshold && sonarState[i]) {
//if we are greater than the threshold and previously were, this is a falling edge:
Serial.print("Sonar ");
Serial.print(i);
Serial.println(" falling!");
sonarState[i] = 0;
}
}
}
The client sends requests at about a 100 millisecond interval, but the server seems to be able to respond much slower than that -- maybe at 2-3 times per second. What's limiting the rate of communication? Is it possible that the serial printouts are actually limiting it? Or does it have to do with how I'm opening/closing/listening to the port in the server code?
thanks for your help!