[chirp_devel] [PATCH] [New Model] Add Support for Retevis RT23 Radio

[Nathan Crapo]

The other thing to try is setting the latency of your USB serial adapter in
the driver advanced tab. I have car tuning gear that requires this.

By default the latency setting is a bit high for a lot of USB serial
dongles. It increases efficiency at the cost of reduced speed. Akin to the
Nagle algorithm in networking maybe?

-Nathan

On Jun 15, 2017 3:26 PM, "Dan Smith via chirp_devel" <
chirp_devel at intrepid.danplanet.com> wrote:

> > +def _rt23_write_block(radio, block_addr, block_size):
> > +    serial = radio.pipe
> > +
> > +    cmd = struct.pack(">cHb", 'W', block_addr, BLOCK_SIZE)
> > +    data = radio.get_mmap()[block_addr:block_addr + BLOCK_SIZE]
> > +    cs = 0
> > +    for byte in data:
> > +        cs += ord(byte)
> > +    data += chr(cs & 0xFF)
> > +
> > +    LOG.debug("Writing Data:")
> > +    LOG.debug(util.hexprint(cmd + data))
> > +
> > +    try:
> > +        for j in range(0, len(cmd)):
> > +            time.sleep(0.002)
> > +            serial.write(cmd[j])
> > +        for j in range(0, len(data)):
> > +            time.sleep(0.002)
> > +            serial.write(data[j])
> > +        if serial.read(1) != CMD_ACK:
> > +            raise Exception("No ACK")
>
> This inter-byte delay timing is rather unfortunate. I assume your
> testing shows that this is the only way the radio will accept the image?
>
> It takes a hair over 1ms to send a single byte at 9600 baud. Sleeping
> for 2ms in between means you're sending one byte every 3ms, which is
> crazy slow. Do you see the factory software actually writing one byte at
> a time in the trace? As we've covered before, doing sleeps at this
> granularity requires the operating system to schedule you pretty
> regularly to keep up the stream, which is both wasteful and error-prone
> of the system is loaded. It also increases the likelihood that the
> driver will behave differently on Linux, Windows, and with differing
> serial hardware.
>
> Have you tried doing something like writing 8 bytes at a time, with a
> sleep in between or something like that?
>
> --Dan
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