From 81c11ba1f71249ef8b3c9bb6d72e65dcda4c6960 Mon Sep 17 00:00:00 2001
From: Martin <25747549+martgras@users.noreply.github.com>
Date: Mon, 25 Oct 2021 21:53:47 +0200
Subject: [PATCH] relax  max entities checking (#2629)

---
 esphome/components/modbus/modbus.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/esphome/components/modbus/modbus.cpp b/esphome/components/modbus/modbus.cpp
index 45c5bfb603..9524f9daf4 100644
--- a/esphome/components/modbus/modbus.cpp
+++ b/esphome/components/modbus/modbus.cpp
@@ -139,7 +139,9 @@ void Modbus::send(uint8_t address, uint8_t function_code, uint16_t start_address
                   uint8_t payload_len, const uint8_t *payload) {
   static const size_t MAX_VALUES = 128;
 
-  if (number_of_entities > MAX_VALUES) {
+  // Only check max number of registers for standard function codes
+  // Some devices use non standard codes like 0x43
+  if (number_of_entities > MAX_VALUES && function_code <= 0x10) {
     ESP_LOGE(TAG, "send too many values %d max=%zu", number_of_entities, MAX_VALUES);
     return;
   }