Windows COM access to PICO via USB trouble

[trossin]

I am able to get serial communication over USB with the PICO when I use putty but when I use a Visual Studio C++ to open the COM port at 115200 baud rate, I can't receive bytes. It does not seem to matter what baud rate I open the port up with putty, it works fine (9600, 2400, 115200). When I do it with my 20 year old code that works just fine with FTDI, or other USB to TTL boards, I can't get any bytes.

Is there some secret that I am missing that putty is doing when it opens the port that I need to add to my windows code. I really don't want to use a USB-to-TTL board when there seems to be a perfectly good USB serial port on the board.

The Open works fine (using COM5,115200,200) but the read does not return bytes.

int CSerialPort::Open(char *PortName, int BaudRate, int ReadTimeOutms)
{
char s[100];

DCB dcb;
COMMTIMEOUTS timeouts;

FillMemory(&dcb,sizeof(dcb),0);
dcb.DCBlength = sizeof(dcb);

sprintf(s,"baud=%d parity=N data=8 stop=1",BaudRate);

if (!BuildCommDCB(s, &dcb)) {
m_hComm = INVALID_HANDLE_VALUE;
CloseHandle(m_hComm);
return(-1);
}

if(!SetCommState(m_hComm,&dcb)){
m_hComm = INVALID_HANDLE_VALUE;
CloseHandle(m_hComm);
return(-1);
}

/* Set time out */

GetCommTimeouts(m_hComm,&timeouts);
timeouts.ReadTotalTimeoutMultiplier = 1;
timeouts.ReadTotalTimeoutConstant = ReadTimeOutms;
if(!SetCommTimeouts(m_hComm,&timeouts)){
m_hComm = INVALID_HANDLE_VALUE;
CloseHandle(m_hComm);
return(-1);
}
return(0);
}

int CSerialPort::Read(unsigned char *data, int NumBytes)
{
unsigned long num_bytes_read;

ReadFile(m_hComm,data,NumBytes,&num_bytes_read,NULL);

return(num_bytes_read);
}

[trossin]

So I grabbed the source for putty and and did some hacking and found that I can get my old Windows code working with this change:

dcb.fDtrControl = DTR_CONTROL_ENABLE;

I hope this helps others if they also run into this problem.

The whole structure is filled like this (The not needed lines are different from what I used to use but did not matter. Just the one line is the key):

dcb.fBinary = true; // Not needed for PICO
dcb.fDtrControl = DTR_CONTROL_ENABLE; // This is needed for PICO.
dcb.fDsrSensitivity = false;
dcb.fTXContinueOnXoff = false;
dcb.fOutX = true; // Not needed for PICO
dcb.fInX = true; // Not needed for PICO
dcb.fErrorChar = false;
dcb.fNull = false;
dcb.fRtsControl = RTS_CONTROL_ENABLE; // Not needed for PICO
dcb.fAbortOnError = false;
dcb.fOutxCtsFlow = false;
dcb.fOutxDsrFlow = false;

dcb.BaudRate = BaudRate;
dcb.ByteSize = 8;
dcb.StopBits = ONESTOPBIT;
dcb.Parity = NOPARITY

[trossin]

I tried those settings with some Silicon Labs USB to TTL converter projects I've built in the past using Microchip 8 and 16 bit processors and found that things got a bit wonky with my dsPIC based logic analyzer project in that it would lock up fetching a block of samples.

https://www.sites.google.com/site/tedro ... ronics/pic

So, Here are the settings that seem to work for the Raspberry Pi PICO USB stdio and the Silicon Labs drivers for the CP210x boards.

FillMemory(&dcb,sizeof(dcb),0);
dcb.DCBlength = sizeof(dcb);

// Need to test with FTDI driver

dcb.fBinary = false; // true in Putty works with SiLabs (Not needed for PICO)
dcb.fDtrControl = DTR_CONTROL_ENABLE; // This is needed for PICO (OK with Silicon Labs driver).
dcb.fDsrSensitivity = false;
dcb.fTXContinueOnXoff = false;
dcb.fOutX = false; // true in Putty but fails SiLabs driver (Not needed for PICO)
dcb.fInX = false; // true in Putty but fail SiLabs driver (Not needed for PICO)
dcb.fErrorChar = false;
dcb.fNull = false;
dcb.fRtsControl = RTS_CONTROL_DISABLE; // RTS_CONTROL_ENABLE in Putty (Not needed for PICO)
dcb.fAbortOnError = false;
dcb.fOutxCtsFlow = false;
dcb.fOutxDsrFlow = false;

dcb.BaudRate = BaudRate;
dcb.ByteSize = 8;
dcb.StopBits = ONESTOPBIT;
dcb.Parity = NOPARITY;

if(!SetCommState(m_hComm,&dcb)){
m_hComm = INVALID_HANDLE_VALUE;
CloseHandle(m_hComm);
return(-1);
}

[trossin]

The settings seem to work with my FTDI interfaces as well so that is what I’ll stick with

[pmulvey]

I had two Picos that connected to my Win 10, 2 months ago. I revisited them this weekend and they would not connect. They connected to Win 8.1 fine but not Win 10. I uninstalled the driver checking "delete files option" and now they are back! While I was trying to figure this out I put CircuitPython on the Picos which connected just fine but was reluctant to use this as I was afraid of frying my brain trying to cope with Micropython on the ESP32 at one end of a radio link and CircuitPython at the other end. My lockdown / retirement project is a Greenhouse and I hope to load it with all sorts of tech, just for the hell of it.