Unable to Upload to Pro Mini using UNO

Official Hardware Classic Pro Mini
1

I'm attempting to upload a sketch to a 5V ProMini using a UNO as ISP, but the sketch will not upload. The IDE output window states:
Using port : COM8
Using programmer : arduino
Setting baud rate : 57600
but does not proceed beyond displaying a small window saying "Uploading" - but it doesn't.

My physical setup is as follows:-
I removed the ATMega328 chip from the UNO and made these connections:
ProMini UNO
GND ----> GND
VCC -----> 5V
RX -------> RX<-0
TX -------> TX->1
GRN ----> RESET (GRN is DTR on my Pro Mini)
The IDE settings are:
Board = Arduino Pro or Pro Mini
Port = COM8
Processor = ATMega 328P, (5V, 16MHz)
Programmer = Arduino as ISP

The ProMini power led lights ok and I've tried swapping the RX and TX connections, just in case. I even tried removing the GRN to RESET connection, but that makes no difference either.

Any ideas as to what I may be doing wrong?

2

A schematic would help, I do not follow word salads very well.

3

My goodness. That's quite the snafu you've created. Where did you get the idea that was going to accomplish anything?

Using the Arduino as an ISP, you upload the ArduinoISP sketch to the UNO to make it act as an ISP.

You connect the UNO's SPI pins (SCK, MOSI, MISO) to the target's ISP pins and one of the UNO's pin (usually 10, if memory serves) to the target's RESET pin.

You've removed the UNO's processor, rendering what's left as little more than a USB to serial converter.

You've conflated using the UNO as an ISP (which uses an SPI connection) with using the brainless UNO as a simple to USB serial converter.

Is there an AI involved in this anywhere by any chance? What you've done has the air of "it sounds right but it's really nonsense" one of those would generate.

4

Don't use rx,tx.

From the UNO side to ProMini.
10 to reset
11 to 11
12 to 12
13 to 13
5V to 5V
Gnd to Gnd

5

@mikedb

I think tha OP only uses the Uno as a serial-to-usb converter, not as a programmer; after all they removed the 328P from the Uno.

6

From your description you are not using the UNO as ISP, but simply as USB-Serial converter - which is a big difference.

You must connect Rx to Tx and vice versa.

I don't understand that. I never saw a Pro Mini with a pin labelled GRN. Did you confuse that with Gnd? All Pro Mini I saw so far label the DTR input as DTR.
But nevertheless you should not use this pin, but connect UNO RST with Mini RST. The capacitor betwenn DTR ans RST is already present at the UNO RSTpin.

7

Tx to Tx and Rx to Rx should be correct, because the communication is between the USB-to-serial converter chip and the processor, not processor to processor.

The sketch would then be uploaded using the usual upload function of the IDE, not "upload using programmer".

8

You are correct, my bad.

9

I always use my UNO to program a pro mini. I leave the 328P in the socket and upload something simple to the UNO, like 'Blink'. You can upload an empty sketch, but basically any sketch is fine as long as it doesn't use pins 0 & 1 or 'Serial' , but you can also remove the 328P.

Then i connect
UNO -> Pro-Mini
5v -> 5v
GND -> GND
TX -> TX
RX -> RX
RST -> RST

So don't use DTR on the pro-min, but use RST instead.
DTR expects a DTR signal, but the UNO's RST does not provide that. The RST pin of the UNO is strong enough to pull the RST pin of the Pro-Mini LOW as well.

10

Pro Mini board has a bootloader program. So, the following connecion between UNO R3 and Pro Mini will make UNO R3 to work as TTL <----> USB converter. As a result, the uploading should be possible if the ATmega328P chip is removed from its scocket and OP selects Pro Mini as AVR Board.

UNO R3 Header Pins       Pro Mini Header Pins
5V                       5V
GND                      GND
RESET                    RESET
RX <-- 0                 RX
TX --> 1                 TX
12

This is the Pro Mini I'm using - actually labelled as Mini Pro, so it's clone really. As you can see, the DTR connection is labelled GRN (top right).

image
image840×435 147 KB

I've solved this issue now though by programming via ICSP instead. These are the connections used with Arduino as ISP loaded to the UNO:
Uno MISO (ICSP Pin 1) → Pro Mini MISO (Pin 12)
Uno VCC (ICSP Pin 2) → Pro Mini VCC (5V or 3.3V, matching the board) (Pin VCC)
Uno SCK (ICSP Pin 3) → Pro Mini SCK (PIN 13)
Uno MOSI (ICSP Pin 4) → Pro Mini MOSI (PIN 11)
Uno RESET (ICSP Pin 5) → Pro Mini RST(PIN RST)
Uno GND (ICSP Pin 6) → Pro Mini GND (Pin GND)

Must learn not to work on stuff when I'm overtired!!

EDIT - Forgot to add, I tried uploading with a 10uF cap from RESET to GND and also without. Both methods worked just fine

13

You never stop learning. I've never seen a Pro Mini like that before.

14

This is what @van_der_decken suggested you in his post #3. So, the solution should be marked on post #3.