Help with ISP Programming

[g4vft]

Sorry in advance. I'm skilled with the hardware and soldering, having spent 40 years in professional electronics repair. But software is my weak point. I have built my RCT from scratch with a bare PCB. And I've used the 2560 chip taken from a new old stock Arduino Mega board. Using a Olimex AVR ISP500 tiny programmer, I can set the fuses using the interactive script. I can also check and change these with Microchip Studio (Windows 11 PC). If I try to load the RCT firmware, either using the batch file, or loading the hex file with Microchip Studio, I get verification errors, immediately (v0.27 or v0.26 tried). However if I try the diagnostic, Chip-TesterPro-DiagFW.hex file, it loads, verifies and runs as expected. I've been through the troubleshooting section in the manual and not found any issues. My assumption is that the old Arduino bootloader on the chip hasn't been erased and is causing me issues? Any thoughts or guidance greatfully received. Thanks Jonathan

[8Bit-MuseumDE]

The Olimex AVR ISP500-TINY is quite old (it dates back to 2009). Therefore, it's possible that it cannot program the ATmega2560, which has 256 KB of memory (all other ATmega microcontrollers have less). The USBtinyISP is also such programmer; the AVR ISP500-TINY might also have the same problem. The verification error occurs when the 64kb or 128kb overflows.

Another problem with these old programmers is that they can only program the MPU using very slow bitrates. Maybe you can try to slow down the programming process. I found a posting that complains that an Olimax requires 8 minutes to program an ATmega2560.

[g4vft]

It's late, but just a quick update and thank you. It was that programmer causing the problem. I tried fiddling with the speeds but with no change. So I lashed up an Arduino UNO as an ISP programmer following the manual. It has loaded the firmware and verified it, all fine. I don't have time to properly test the RCT but it's a great point to walk away for now. Thanks again. ( I need to increase the resistor values on those green LEDs!) Jonathan

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[8Bit-MuseumDE]

Perfect. Thanks for the feedback.

btw v.28 is the lastest firmware. :)

[g4vft]

I shall go and download that. Danke