From: Don Kuenz <mail@crcomp.net>
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Date: Mon, 16 Nov 2020 06:21:56 -0800
Subject: [PIC] An In-Circuit Serial Programmer application
Thread-Topic: [PIC] An In-Circuit Serial Programmer application
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=20
Brent wrote:

<snip>

> IMHO the ICSP circuit can be simpler yet remain effective i many cases...=
 just a
> single pull up resistor to VDD. Value of 10k works well for me, using ICD=
3 and
> ICD4. The resistor must present not too great a load to the programmer du=
ring HV
> programming mode, nor push up VDD appreciably. Conversely it must be low

> P.S. - It also works well with a Bootloader.
> use the ICSP interface to install the TinyBootloader or an equivalent wit=
h
> the ICSP Dat and Clk lines set at the Rx and Tx lines and you have a nice
> development device with Programming, Debugging and Communications all
> achieved via a USB/Serial adapter - Great to hand out to students or use
> for casual experimenting as well as in target applications.
> enough value to prevent unwanted MCLR pul downs by noise. A couple of bas=
ic
> tips: keep traces short around ICSP, and don't expose VDD to the outside =
world
> where it can pick up noise. In most cases the RC reset circuit is no grea=
t loss with
> most PIC's having fairly decent internal power up & brownout reset genera=
tors that
> can be enabled.
>
> Yes ~ a bootloader is indispensable once you have settled on a good one. =
All going
> well you then only need to use ICSP once... so isolation becomes less imp=
ortant. I
> prefer a bootloader that doesn't require a button press, DIP switch, or j=
umper, to
> initiate it... these are time consuming and annoying steps during develop=
ment
> code/program/debug cycles (frequent for me), and a complication when doin=
g field
> updates. Ideal: bootloader runs for a brief time at reset and invokes loa=
ding if
> detected else runs application, optionally add hardware reset capability =
by using
> e.g. the RTS line, and/or have the application code invoke the bootloader=
 after
> receiving a serial escape sequence (unless this presents an unacceptable =
security
> risk).
>=20
> Nice work on the web page though, good circuit design/description. I skip=
 read it
> and only noticed a missing "be" in 4th pragraph "can not left unused".

Your successful experience with using a single pull up resistor and
dropping the diode and capacitor confirms my suspicion the old=20
Guideline's mostly a historic artifact. This thread gives me plenty to=20
think about.
    The typo on the webpage's now corrected. My website attempts to
follow an ARRL format with its projects. It's my goal to push my lab=20
notes out to the web.

Danke,

--=20
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

--=20
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