SAMA5D27-SOM1 module stuck on RomBOOT, unresponsive otherwise - Page 1
Forum section: electronics / general

author: daqq
author_rank: Super Contributor
timestamp: June 12, 2022, 08:30:17 pm
content: Hello,I'm playing around with a custom board built around the SAMA5D27-SOM1 ARM module (https://www.microchip.com/en-us/product/ATSAMA5D27-SOM1). When powered on the board gets stuck on sending me "RomBOOT" through the default USART @ 115200, every 20 seconds or so. It does not respond to SAMBA commands sent through the USART, enumerate on the USB or give any reaction. The power consumption of the board is not unreasonable, there's no obvious overheating.The module is brand new from a reputable supplier, though has been in storage for a few months before soldering. I have checked, there are no shorts between adjacent pins of the module. There is no visible damage to the module itself.I've checked the internal module voltages as per the troubleshooting guide (http://ww1.microchip.com/downloads/en/Appnotes/AN_3379%20-%20SAMA5D27-SOM1%20Auto-Test.pdf), no issues. I've checked both external and internal QSPI bootable memories with a scope - nothing is happening, no bit twiddling, nothing. The external memory is empty and there's no bootable code there. Not sure about the internal one, but the bloody thing doesn't even try to communicate with it (no CLK activity, no CS activity).I've checked the module 24MHz crystal with a scope - this is a bit iffy, it's possible that I've loaded the oscillator too much with my probe, but I do not think so - I've tried both non-contact and contact measurements, there's no oscillation.The 32kHz crystal is running funnily enough.NRST is working fine - pulling it to ground with a button gives me the RomBOOT message.I've tried pulling the WKUP pin high and low, nothing.All of the JTAG signals are pulled high and nothing is connected to them.Tomorrow I'm gonna populate another board with the module only, with only the minimal pins connected, but I am vexed.Frankly, I'm stumped.Any ideas on how to proceed further?Thanks,David

author: benSTmax
author_rank: Regular Contributor
timestamp: June 13, 2022, 04:05:02 pm
content: Do you have the SD card pins available? If yes, can you try to boot one of the provided images for this module from a SD/microSD card?

author: daqq
author_rank: Super Contributor
timestamp: June 13, 2022, 08:11:51 pm
content: Thanks for the reply. Would it be worth trying given the overall unresponsiveness? I do have them on the board on test points, just in case, could hack a quick socket...

author: benSTmax
author_rank: Regular Contributor
timestamp: June 13, 2022, 09:21:20 pm
content: Some years ago I played with SAMA5D2 and Linux and I remember the boot sequence to vary with the part revision.I remember there was a rev B and C which had different boot behavior.Anyway, SAMA5D27-SOM1 is newer and I assume being a rev C at least. If the Card Detect pin is low on any of the SDHC card interfaces (there are 2 of them), the rev C would normally try to boot from the one with its CD pin low.It checks first SDHC1 (if CD is low) and then SDHC0.Just to avoid soldering a SD/microSD adapter, try first to have Card Detect pin low and then power up the board. See if you get any activity on the SDHC I/O pins used to communicate with the SD/microSD card. If you see activity then it is worth making the next step and solder a SD/microSD connector to try to boot from a card

author: daqq
author_rank: Super Contributor
timestamp: June 14, 2022, 06:32:37 am
content: Okay, I can try, but what will that mean for my normal design? Without an SD Card it's useless and will never boot up?

author: benSTmax
author_rank: Regular Contributor
timestamp: June 14, 2022, 04:53:23 pm
content: You said the module was new, therefore if the fuse bits haven't been messed up with it should allow you to boot from other devices than SD/microSD cards

author: daqq
author_rank: Super Contributor
timestamp: June 18, 2022, 07:24:32 am
content: Thanks! Problem traced to SD CARD detect pin on one of the SDMMC interfaces being pulled low. There was nothing on the rest of the interface and the MCU probably got stuck on trying to read out a non-existing card

author: benSTmax
author_rank: Regular Contributor
timestamp: June 19, 2022, 10:13:32 am
content: Great to hear you have it in good working condition